阅读说明：本技术 颤音臂及系统 (Trill arm and system ) 是由 彼得·约瑟夫·沃尔克 于 2016-03-21 设计创作，主要内容包括：公开了一种手动颤音控制装置,系统和处理装置。一种手动颤音装置包括一个可旋转的轴,所述轴上的凸起的凸轮部分,容纳在轴上的凸轮部分两侧的第一和第二偏置轴环,第一轴环的偏压与第二轴环的偏压成反向旋转,使得当轴沿一个方向旋转时,其接收来自第一轴环回弹力但不旋转第二轴环,反之亦然。还公开了处理技术,以从轴上的旋转传感器,优选为霍尔效应,获取旋转数据,并且生成用于音高修改装置的音高变化指令。映射是用户可控的,以产生期望的效果和性能。(A manual vibrato control device, system and processing device are disclosed. A manual vibrato device includes a rotatable shaft, a raised cam section on the shaft, first and second biasing collars received on either side of the cam section on the shaft, the bias of the first collar being counter-rotating to the bias of the second collar so that when the shaft rotates in one direction it receives a return force from the first collar but does not rotate the second collar and vice versa. Processing techniques are also disclosed to acquire rotation data from an on-axis rotation sensor, preferably the hall effect, and generate pitch change instructions for a pitch modification device. The mapping is user controllable to produce the desired effect and performance.)

1. A manual vibrato control device adapted to generate rotation data for an electronic pitch modification device, characterised in that the device comprises a rotatable shaft, a raised cam portion on the shaft, first and second collars received on the shaft either side of the cam portion, each collar being rotatable relative to the shaft and having a resilient bias urging it towards a central position, wherein the bias of the first collar is counter-rotating to the bias of the second collar, the first and second collars and the cam portion engage at respective surfaces, such that when the shaft is rotated in one direction, which receives a return force from the first collar but does not rotate the second collar, and such that when the shaft rotates in a second, opposite direction, it receives a return force from the second collar but does not rotate the first collar.

2. The device of claim 1, wherein the device includes first and second torsion springs to provide the resilient bias to the first and second collars.

3. The apparatus of claim 1, wherein the shaft includes a rotation sensor such that operational rotation of the shaft causes the rotation sensor to generate data regarding the degree and direction of rotation.

4. The device of claim 1, wherein the shaft is adapted to be connected to a vibrato control device for operation by a musician.

5. The device of claim 1, wherein the device is adapted to be secured to a musical instrument.

6. The apparatus of claim 3, wherein the rotation sensor comprises first and second magnets disposed in or adjacent to the shaft, the first and second magnets having opposite polarities, and a Hall effect sensor that is stationary with respect to rotation of the shaft such that the magnets rotate with the shaft, and the Hall effect sensor measures changes in the value and polarity of the magnetic field to produce rotation data indicative of the rotational position of the shaft.

7. An apparatus according to claim 3, wherein the rotation data is output to a processor, the rotation data being output to a processor, the processor processing the rotation data to produce data indicative of a desired degree of pitch change.

8. The device of claim 1, further comprising an attachment for holding a guitar string disposed along the shaft.

9. The apparatus of claim 8, wherein the appendage is disposed between the first and second cam portions.

10. A device according to claim 7, further comprising pitch modification means.

11. A method for returning a manual vibrato device to a central position, the manual vibrato device including a rotatable shaft, a raised cam portion on the shaft, first and second collars received on the shaft on either side of the cam portion, each collar being rotatable relative to the shaft, the method comprising:

a) providing a resilient rotational bias to the first collar urging it towards a central position; providing an opposing resilient rotational bias to the second collar urging it towards a central position;

b) providing shaped engagement surfaces on the cam portion and respective surfaces of the first and second collars;

c) such that when the shaft rotates in one direction it receives a return force from the first collar but does not rotate the second collar; and such that when the shaft rotates in a second, opposite direction, it receives a return force from the second collar but does not rotate the first collar.

12. The method of claim 11, wherein the rotational bias for the first and second collars is provided by respective first and second torsion springs.

13. A method according to claim 11, wherein the manual vibrato device is adapted to produce rotation data for an electronic pitch modification device, and the device further comprises a rotation sensor, such that operational rotation of the shaft causes the rotation sensor to produce data relating to the degree and direction of rotation.

Technical Field

The present invention relates to providing a tremolo function to a musical instrument, particularly a stringed musical instrument such as a guitar or the like.

Background

Over the past 70 years, guitars have been an important instrument in western popular music. Electric guitars are widely used and modified and the output signal is subjected to various electronic modifications. For example, many of the unique effects played by an electric guitar player are the result of using specially designed pedals and other modifying equipment. These devices, coupled with the skill and ability of the artist, enable a variety of effects, sounds, and styles of performance.

Another aspect of the playing dynamics of many guitars is the use of a crank or tremolo arm. This allows the pitch of the note to vary relative to the normal value of the note. This term is widely used in stringed musical instruments, for example in connection with violins, and in connection with human sounds. It is noted that in many cases, this assembly is incorrectly referred to in guitars as a tremolo arm, a tremolo being actually a change in amplitude rather than a change in pitch or frequency. The present invention relates to providing tremolo devices for guitars and other musical instruments.

Tremolo devices for electric guitars have been known since the thirties of the twentieth century and have begun to be widely used during the fifties and sixties of the twentieth century. The vibrato arms currently in use are all mechanical in nature. Essentially, they use a mechanical system to change the pitch of the string to reduce or increase the tension of the string, thereby reducing or increasing the pitch accordingly. Changing pitch in this manner has some inherent disadvantages.

A particular problem is that when the tremolo arm is released, any or all of the strings may not return to the full correct pitch. The pressure of the strings, the inherent error in the return to positive mechanical design, and the possibility of the strings winding around the bridge or bridge during handling are the root causes of this problem. These factors may produce unwanted variations in string tension that affect tuning of the instrument. Correct tuning is associated with high precision and technical understanding, which is complicated by the requirement that the instrument must be correct in absolute pitch while all strings on the instrument maintain precise relative pitches. This complicates the tuning process, wherein errors are particularly noticeable when two instruments are played simultaneously, since in this case any differences will be more noticeable.

Tension variations inherent in the operation of the tremolo arm also cause stress on the neck, strings and body of the instrument. This limits the extent of pitch changes possible and the type of instrument on which the tremolo stick can be mounted. For example, the mechanical and structural requirements of the tremolo system often make the tremolo stick unusable for acoustic guitars.

Various attempts have been made to solve these problems, for example as outlined in http:// en. wikipedia. org/wiki/Vibrato _ systems _ for _ guide. These include a suspended bridgeRotary chords (Bigsby), locked strings (Floyd Rose), multi-lever systems (Wilkinson et al).

Although an improvement in some respects over prior art systems, all of these systems require the application of complex mechanical systems, simply to compensate for the mechanical deficiencies of the vibrato.

More recently, electronic devices controlled by foot pedals or switches have allowed pitch changes to be applied to the output of an electric guitar, which is typically done using Digital Signal Processing (DSP) methods. While such systems are capable of producing pitch changes, the artist using a foot pedal or switch cannot achieve the level of precise control or performance provided by the tremolo arm. Furthermore, foot control method-pedal up: unchanged, pedal down: maximum variation-only allowing pitch variation in one direction at a time. This limitation is inherent in the switch control.

Some of the disclosures in the prior patent documents disclose the principle of using a mechanical vibrato arm, thereby providing control over the electronic pitch control device and thereby providing the advantages of a mechanical, manually controlled vibrato mechanism, without mechanical connection to the strings of the instrument.

For example, US 5631435 to Hutmacher discloses a photosensor for the movement of a mechanical tremolo arm that is held between the tensions of coil springs to allow the arm to return to a centered position.

U.S. patent No.7049504 to Galoyan discloses an arrangement that uses a shaft and torsion spring to return the vibrato arm to a central position. In this case, the rotation of the potentiometer is used to sense the position.

WO 2005104089 to Ruokangas et al discloses the general idea of how to mechanically operate the vibrato arm and control the vibrato using an effector. The disclosed vibrato arm uses a compression spring and various sensors to control the rotational position of the arm.

None of the above patent references appear to have emerged in commercial use. In all aspects, all of these disclosures do not define a system capable of being precisely repeatedly operated by a player.

An object of the present invention is to provide a tremolo device capable of being accurately repeatedly operated by a player.

The reference in this specification to any prior publication (or information derived from it), or to anything known, is not, and should not be taken as, an acknowledgment or any form of suggestion that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Disclosure of Invention

In a first broad form, the invention provides a vibrato control device having an arm and a sensor for detecting a position of the arm. The position data is sent to the control means which processes the data to provide input to the pitch control means.

In one aspect, the invention provides a manual vibrato system including a manually operated vibrato control device with an arm, a rotation sensor that senses rotation of the arm and produces rotation data, and a processor that receives the data and is adapted to send pitch change instructions to a pitch modification device.

According to another aspect, the invention provides a method for providing vibrato, the method comprising receiving rotation data from a manually operated vibrato control device having an arm, the rotation data being indicative of rotation of the arm, and processing the rotation data to provide pitch change instructions to a pitch modification device.

According to another aspect, the present invention provides a manual vibrato control device for use with an electronic pitch modification device, wherein the device includes a rotatable shaft, a raised cam section on the shaft, first and second collars received on the shaft on each side of the cam section, each collar being rotatable relative to the shaft and having a resilient bias urging it towards a central position, wherein the bias of the first collar is counter-rotating to the bias of the second collar, the first and second collars and the cam section engaging at respective surfaces such that when the shaft is rotated in one direction it receives a return force from the first collar but does not rotate the second collar, and such that when the shaft is rotated in an opposite second direction it receives a return force from the second collar but does not rotate the first collar.

According to another aspect, the present invention provides a manual vibrato control device including a rotatable shaft, an arm received on the shaft, two magnets arranged in or adjacent to the shaft and having opposite polarities, and a hall effect sensor stationary with respect to rotation of the shaft such that the magnets rotate with the shaft, and the sensor measures changes in the value and polarity of the magnetic field to produce rotation data indicative of the rotational position of the shaft.

According to another aspect, the present invention provides a method of sensing the position of a rotatable shaft, the method comprising providing two magnets arranged in or adjacent to the shaft and having opposite polarities; a hall effect sensor is provided which is stationary with respect to rotation of the shaft such that the magnet rotates with the shaft, the sensor measuring changes in the value and polarity of the magnetic field, thereby producing rotation data indicative of the rotational position of the shaft.

According to another aspect, the present invention provides a manual vibrato control device including a rotatable shaft, a raised cam section on the shaft, a first collar received on the shaft and engaging the first cam section, a second collar received on the shaft and engaging the second cam section, each collar being rotatable relative to the shaft and having a resilient bias urging it towards a central position, wherein the bias of the first collar is counter-rotating to the bias of the second collar, the first and second collars and the first and second cam sections engaging at respective surfaces such that when the shaft is rotated in one direction it receives a return force from the first collar but does not rotate the second collar, and such that when the shaft is rotated in an opposite second direction it receives a return force from the second collar but does not rotate the first collar.

Embodiments allow a mechanism to provide a back-centering function in a reliable, precise manner that does not rely tightly on the bias applied to the first and second collars, wherein the bias is identical.

Accordingly, embodiments of the present invention allow for an accurate and precise centering mechanism and provide reliable position information to the collected. The processing of the positional data and user selectable parameters allows for a player-centric vibrato system that is fully electronic in processing, yet retains excellent player control and dynamics capabilities.

Drawings

Illustrative embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 shows an overall view of an embodiment of the invention with a guitar;

FIG. 2 schematically illustrates a similar arrangement to FIG. 1, but using a wireless connection;

figure 3 illustrates in partially exploded view an embodiment of a vibrato arm in accordance with the present invention;

FIG. 4 shows a further exploded view of the arm of FIG. 3;

fig. 5 shows a photograph of an assembly device similar to fig. 3 and 4;

FIG. 6 is a schematic view of a zero region in operation of an illustrative arm;

FIG. 7 is a schematic view of the zero and edge regions in operation of an illustrative arm; and

FIG. 8 is a flowchart showing pitch direction changes;

FIG. 9 is a flow chart illustrating null detection;

fig. 10 is a flowchart showing the TZ region processing;

FIG. 11 is a flow chart showing readjusting pitch control;

FIG. 12 is a flow chart showing control of maximum and minimum pitch changes;

FIG. 13 is a flow chart illustrating control of arc reconditioning;

FIG. 14 is a flow chart showing readjustment to the MIDI scale;

fig. 15 is a flowchart showing overall process control for the embodiment of the present invention.

FIGS. 16A and 16B are views of a mount for a device according to the present invention; and

fig. 17 is a side view, partially in section, of an alternative embodiment of a mechanical vibrato.

Detailed Description

The following examples and embodiments are intended to be illustrative and not limiting. It is important to note that various inventive concepts have been disclosed that can be used together or separately in many cases and which offer significant advantages over prior devices. Accordingly, the components of the entire illustrative embodiment may be used alone or in various combinations thereof. In particular, implementations may include some or all of the software features described.

In the drawings, like reference numerals are used to designate like parts that appear in the drawings.

The invention will be described primarily with reference to a 6-string electric guitar and an acoustic guitar. It can be applied to 4, 6, 7, 8 or 12 string guitars. However, the invention is suitable for implementation by using other musical instruments, in particular stringed musical instruments such as bass guitars, mandolins and other forms of guitars and similar instruments. With appropriate modification, the aspects of the present invention can be applied to any desired musical instrument.

It should also be appreciated that although the present invention is primarily described with reference to additional apparatus, aspects of the present invention may be integrated with other devices at the time of manufacture. For example, the tremolo arm may be mounted to the guitar during manufacture, or the tremolo box may be integrated into the guitar, amplifier, effects or pitch control unit. However, for convenience and clarity, these will be described as elements added to an existing guitar setup.

The described system is envisaged for use with a conventional electric guitar. Guitars have an associated amplifier and, in most cases, one or more effect pedals or other devices to modify the output of the guitar or amplifier. These conventional aspects need not be changed and will not be discussed in detail. The present invention may be applied to any conventional guitar or related accessory. In particular, the present invention can be applied to acoustic instruments as well as electronic instruments.

The invention has several aspects that are particularly useful for ensuring that the vibrato arm returns to the correct position and that small changes (as will be explained in more detail below) are managed and processed in sequence by the software to produce the musical result that the player wants to achieve.

Other aspects are directed to features that enable improved performance, and provide additional options and features that players utilize.

Fig. 1 generally shows the application of a tremolo device 10 according to the invention to a guitar. The tremolo device 10 is secured to the guitar 39 at a location behind the bridge of the guitar 39. The tremolo device 10 includes an arm 20 adapted to rotate, as will be explained further below.

The guitar is shown connected to a pitch control device 36 via a conventional lead 33. Which in turn is then output to amplifier 38. The tremolo device 10 is connected via a wire 31 to a control box 30, which control box 30 in turn is connected to a pitch control unit 36 via a MIDI connection. It is emphasized that in the preferred embodiment, the tremolo device 10 and control box 30 are not in any way interposed between the guitar and the amplifier. Thus, when the pitch control unit 36 is in the true bypass mode, the guitar signal will go directly to the amplifier.

In an alternative embodiment shown in fig. 2, the tremolo device 10 includes a wireless communication system 31A, such as bluetooth or Wi-Fi. A suitable receiver 30A is provided on the control box 30 so that data from the vibrato device 10 may be wirelessly transmitted to the control box 30. It will be appreciated that in such an embodiment, the tremolo device may require a battery.

It will be appreciated that the fixing arrangement is purely for stabilising the arm so that the device can be played. The torsion spring does not exert any load like a conventional tremolo system, wherein the player overcomes in one way or another the combined tension of the guitar strings and the heavy return spring of this mechanism. The structural requirements are thus minimal, since no great pressure is exerted on the tension of the strings that need to be supported by the guitar. Thus, this system is well suited for lighter construction instruments, such as acoustic guitars and other stringed musical instruments.

The universal mount may be adapted for use on any guitar, whether an electric or acoustic guitar. Referring to fig. 16A and 16B, the mounting bracket 50 can be seen. In fig. 16A, the lower surface 52 secured to the guitar is visible, as well as the adhesive area provided by double-sided tape or other suitable technique. Due to the internal design of the moving part of this embodiment, the adhesive tape does not have to withstand high separating forces. The moment is distributed so that the required adhesive force is relatively low.

In fig. 16A, the upper side of the mount is visible. The underside of the body of the tremolo device according to this embodiment has a groove which slides into a beautiful track 54 on the mount. This arrangement has the advantage that multiple mounts can be attached to different guitars so that the tremolo device can be moved as desired. Alternatively, the guitar may include an integrated mount. Of course, in suitable embodiments, any desired mount may be used.

Fig. 2 shows the connection between the tremolo device 10, the control box 30, the guitar and the pitch changing device. The illustrated embodiment uses a vibrato control box 30 to receive signals from the vibrato device 10 (as described below) and process these signals to generate data for the pitch-changing device 36.

In a preferred embodiment, the pitch change device is a commercially available device, such as Digitech Whamy V.for accepting MIDI (musical instrument digital interface) input. MIDI is a well-known protocol for connecting a musical device, such as a keyboard, to an electronic unit, such as a sampler. This protocol is well understood and widely practiced in the industry and is described in more detail in, for example, http:// www.midi.org/techspecs, the contents of which are incorporated herein by reference. Since this is actually an industry standard, it will not be disclosed in further detail.

Of course, while this is a preferred arrangement, other modes and techniques may be used to connect the control box 30 to the pitch-shifting device 36 in addition to the MIDI method described.

The MIDI protocol includes program changes-changing from one program to another in a switching manner, and control changes-which allow (analog/proportional) value changes to be sent and decoded. The control box 30 uses both aspects.

The control box 30 contains a microprocessor, such as ATmega328 by Atmel. The processor has an internal analog-to-digital converter that is necessary to convert the variable voltage of the sensor to digital data for processing. The control box also comprises a switch and an LED indicator light for user control and state feedback. The microprocessor is preferably adapted to output the MIDI signal to the pitch change device, but may also be adapted to other output formats, such as Control Voltage (CV), RS232/485 serial, etc.

In summary, the operation of the control box is as follows:

1) the sensor detects the movement of the tremolo rod.

2) The sensor generates a variable analog voltage proportional to the motion.

3) The microprocessor converts the analog voltage to digital data.

4) The microprocessor uses algorithms to modify the data to provide various operating characteristics and enhancements.

5) The data is formatted to match the control method of the selected pitch-shifting DSP, in this case MIDI data, before passing on to the next stage.

It should be noted that the nature and origin of the analog voltages will be explained further below. The process is applicable to the following various rotation/motion detection methods; sensor and mounting geometry; a microprocessor; and outputting the format requirement.

The control box 30 has power filtering and conditioning so that it can be powered from any standard 9Vdc instrument plug set. Battery operation is also feasible due to lower current requirements (<40 mA).

The control unit 30 also has various setting switches. One set of switches allows the user to define limits of pitch change when the lever reaches its highest deflection above or below. This means that the player can be relieved of the fact that when the arm is moved to the limit it will be well at the specified pitch. Thus, regardless of the skill level of the player, he can always use vibrato to achieve a given pitch change.

The pitch limit may be selected independently for "up" pitch changes and "down" pitch changes. In a preferred form, a series of selectable preset pitches are provided, with the maximum pitch variation associated with a particular style of music in each direction. Of course, other embodiments may provide other mechanisms to control this aspect.

For ease of operation, these user pitch presets are grouped into two "modes" A and B, selectable by tethering the foot pedal to the control unit. This facilitates the user to change the "personality" of the percussion effect during the performance. As an example, mode A may be a combination of small pitch changes and mode B may be a combination of larger pitch changes.

It will be appreciated that in other embodiments, different methods may be used to control pitch preset and other features, such as a PC interface, a network interface or an application program interface connected to a tablet, smartphone or other device.

After processing the data, the microprocessor sends its output to a simple circuit to convert its 5v digital output into a 5mA balanced current loop, all MIDI devices, including the electronic protocols used in the MIDI devices used in this embodiment.

The guitar audio signal is not connected to or passes through the control box 30. The guitar audio only passes through the pitch change device 36 under the control of the control box 30. Another foot switch on the control unit (not shown) sends a signal to instruct the pitch-shifting device 36 to enter the bypass mode (where the pitch processing is suspended). The bypass and mode select switches have LED indicators to show the user their current status.

It will be appreciated that this embodiment is independent and independent of the manufacture/model of the guitar or amplifier.

Sensing of the rotational position of the vibrato arm 20 is a key aspect of the effective operation of any vibrato system. The ability of the artist to produce a full range of desired effects depends on accurate and precise determination of the rotational position of the vibrato arm 20. We will now describe one aspect of the invention that relates to using hall effect sensors to sense position using magnetic field movement. It will be appreciated, however, that the present invention may use a different sensor system in combination with the vibrato arm 20, or such sensor arrangements in combination with other constructively different arms of the vibrato control arrangement.

The Hall Effect (HE) sensor is located on the PCB 9 (see fig. 3, 5). For such an implementation, this would have to be a proportional Hall effect device to produce a proportional output, rather than a binary "yes/no" output common to some HE devices. One suitable example is Allegro Micro A1302, which requires only one reference voltage (provided by a 5Vdc power supply), ground and output connections. The HE device output is a varying analog voltage proportional to the magnetic polarity and field strength.

The two magnets 6, 6A are preferably neodymium disk type rare earth magnets of field strength around 4000-. These are generally available. They are mounted with opposing magnetic fields and are disposed at offsets on either side of a central reference on the spindle, i.e. in recesses 13, 12. Thus, a substantially linear magnetic field is generated around them. HE device is not visible, but is mounted on the front face of PCB 9 to face magnets 6, 6A. This is best seen in fig. 5. As the spindle moves, the magnet moves and the magnetic field moves relative to the HE device, which thus measures a variable magnetic field value and its change in polarity, thereby producing a variable electrical output. It is important that the HE device is sensing the combined flux field established between the substantially linear magnets, rather than sensing the absolute flux level sensed from one magnet (in general) and its different proximity to the HE device. Thus, the HE device outputs a rotational position representing the spindle (itself moved by the arm) in both rotational directions with respect to the center position.

The angle of displacement of the magnets on the shaft is directly related to the degree of movement required for the vibrato arm. They are arranged so that the arm motion/spindle rotation at its maximum can provide the HE device with sufficient field strength and polarity change to ensure that it reaches maximum and minimum voltage outputs. The distance between the main axis of rotation and the HE device is fixed because it is disposed adjacent and tangential to the main axis.

The specified field strength of the magnet, in combination with the displacement angle of the magnet and the fixed spindle/sensor relationship described earlier, ensures that the HE device generates a full-scale output between the maximum arm positions, which are fully up and fully down. For the convenience of the user, the full scale value is not used in practice because the process limits pitch changes to an operating interval less than the maximum arm displacement, as described elsewhere.

As a result, processing requires only a subset of values from the full range of available data values. This has the advantage of providing a good signal-to-noise ratio in the system and making the mechanism more tolerant to manufacturing and assembly tolerance drift, magnetic field strength variations, HE device capabilities, etc. The described sensing method provides a contactless, wear-free sensor system of linear output.

The PCB 9 obtains its power and reference voltage from the control unit via a three-wire cable. The cable also transmits the output voltage back to the microprocessor for a/D conversion as previously described. Many DSP pitch change devices require a change of mode in order to switch between pitch up or pitch down. This is generally because the algorithm of (high quality) pitch processing is specific to each direction of pitch change, up or down. Real-time pitch processing belongs to a highly subtle field of mathematics, using complex processing. As mentioned above, the preferred embodiment of the present invention relies on an off-the-shelf pitch variation device. Such commercial products are similar to many other pitch changing devices in the musical instrument field-they do this by providing a user with a toggle or rotary switch to select the desired function, raise the pitch or lower the pitch.

The control box 30 of this embodiment dynamically detects which "pitch change direction" is required by analyzing the input data stream in relation to the nominal centre (zero-pitch) value. If it is determined that the pitch change direction has changed, it will send the appropriate MIDI program change command to the DSP to set it to the desired pitch pattern, up or down.

Figure 8 illustrates the software operation of this feature in the control box 30. The sensor data 60 is read. This value is evaluated relative to the central, zero pitch value. If the arm is at the center value (i.e., if the sensor data corresponds to the center position), it sends a 0 pitch change command 63. If the value is higher, the pitch change is set to UP, a value of 62; if lower, it is set to 64. Other processing is then complete (as described below) and a new pitch change request is sent to pitch change device 36.

The control box 30 performs various data processing to provide user features and functions as described elsewhere. Its final output in this embodiment is adjusted and mapped to meet the requirements of the MIDI protocol, i.e. the control change command is only available between values of 0-127, since MIDI uses a variable representation of 7 bits. Remapping and scaling is a simple function that can be easily changed to meet the requirements of other pitch change DSPs.

Fig. 14 shows a remapping process. The sensor values are read at 70 and the required processing of pitch changes etc. is performed at 71. At 72, the determined pitch change value is rescaled to the 7-bit MIDI scale. The request is then sent to pitch change device 36 at 73.

In this embodiment, the tremolo device 10 is connected to a control box 30, which control box 30 is in turn connected to a pitch variation device, which in turn is connected to the output of an amplifier or other arrangement. However, it will be appreciated that the control box 30 may be incorporated into the pitch control unit, for example, or otherwise connected in a different topology or arrangement to provide the described features. For example, the functions of the control box may be integrated into a connection line for the pitch changing device or a portion of a dongle.

Furthermore, although the apparatus is described using conventional connecting wires for ease of description, it will be appreciated that any suitable connection or communication means may be used, for example a wireless connection such as wifi, optical network or other protocol sufficient for data requirements.

Fig. 3 shows the mechanical operation of an embodiment of the tremolo device according to the invention. Fig. 4 shows the same embodiment in a larger development, and fig. 5 is a photograph showing the assembly device according to this embodiment with the cover removed.

The tremolo device 10 includes a main shaft 5 that extends through the length of the device 10. The main shaft 5 has a substantially cylindrical shape forming a shaft, provided with an enlarged substantially protruding portion 15 near the longitudinal center. This includes angle cams 14, 15, which will be described in more detail below. The raised portion 15 further comprises recesses 12, 13 for receiving the magnets 6. Once the rest of the tremolo device 10 is assembled, the cover 1 is in place.

At each end of the main shaft there is a collar 7 and 4. They are free to rotate about the main shaft but are limited to their maximum rotation by respective end stops 17, 19 (indicated but not visible) in the housing 8 and end chassis 2 respectively. Each collar has an associated torsion spring 3, 3A. These springs are connected at one end to their respective collars 4, 7 and at the other end to the mounting recesses 8, 18. The spring and the collar are connected such that they are resiliently prevented from rotating. They are installed under some tension during manufacture, even when the mechanism is in its central position.

An arm 20 is connected to the end of the spindle 5. The arm 20 includes a pivot 21 to allow the angle of the arm to be adjusted to suit the player.

When assembled, the entire mechanism is largely located within the housing 8, with the chassis support 2 at the same end as the arms 20. It can be seen that the PCB 9 and associated sensors (not visible) are located alongside the magnets 6, 6A in the assembled state, the magnets 6 being visible in fig. 5. This facilitates the operation of the hall effect sensor described above.

The key mechanical requirement is that the arm 20 be able to rotate smoothly to the desired position and return to the center (RTC) with high reliability and accuracy. The center is where there is no pitch change required and the guitar is working properly.

The shaping of the cam surfaces 14, 16 on the spindle 5 is an important component of the operation of the RTC mechanism. The collars 4, 7 are coaxial and free to rotate, but when subjected to spindle rotation, transmitted by the spindle cams 14, 16, they rotate in opposite directions. At the same time, the collar is stretched by the torsion spring 3, 3A. These springs have a triple function:

they provide resistance to the user to "resist" the arms, providing tactile feedback. When the vibrato arm is in rest, they perform a precise central position, while when the vibrato arm is released they return the spindle to a zero-pitch-variation position (with high precision and repeatability).

The blocking function is completed as a result of the spring resisting rotation of the collars 4, 7. Each cam surface 14, 16 of the spindle is in close contact (whether rotating clockwise or anticlockwise) with a surface of the corresponding collar 4, 7. Thus, the main shaft experiences the same (bi-directional) rotational resistance as the collar.

Furthermore, the shape of the cams 14, 16 provides an obstacle to prevent the collars 4, 7 from rotating further than their respective neutral positions. The positioning of these mechanical "end stops" can be precisely defined during the manufacturing process to return the two chucks to a constant position.

The net effect is that the spindle 5 always returns to a fixed, neutral position with high accuracy and repeatability. The RTC process is not a tolerance constraint. The springs do not have to be perfectly matched (only if the cost is quite high, this is possible) because the RTC factor is not dependent on this aspect. The springs are preferably "over-specified" so that they retain sufficient torsional strength when used for an extended period of time.

Furthermore, the preload of the spring can be set in manufacture to ensure that it will overcome most of the hysteresis in the friction components inherent in any mechanical RTC mechanism.

It will be appreciated that the invention may be implemented using any suitable material. To allow operation of the hall effect sensor device, it is preferred that the material be non-magnetic.

Illustratively, the shaft/spindle arrangement, arms and housing are made of machined aluminum. The collar is machined nylon. The chassis is made of a machined nylon composite. All parts can be suitably manufactured by CNC machining.

A particular concern with the return-to-center (RTC) mechanism of vibrato systems is to meet the requirement of very high accuracy, since even at the center (or "zero") position, the listener can detect small pitch errors. Any tuning differences are particularly noticeable with respect to other instruments that are still at the correct reference pitch.

In the performance, musicians first agree to tune their instruments to a reference pitch. If the instrument is slightly out of tune due to this type of RTC error, the pitch control device may not be usable even if it is nominally useless (i.e., in its rest position, a "zero-pitch-change" command may be sent to the pitch processor).

There are many other rule/algorithm based functions in the embedded software in the control box 30 that contribute to the efficient operation of the vibrato system.

The control system uses the current value of the rotational position to set the nominal center value when the power is turned on. This will take into account small variations in the central value due to wear, temperature, magnetic field strength variations, etc. If a "meaningless" value is detected (i.e., outside the defined range), the center value is retrieved from flash memory contained within the preferred processor. The initial center value is measured/stored at the time of manufacture.

In mechanical tremolo systems there is a degree of tilt or free movement around the center, which is usually associated with arm coupling. A minimum rotation of the tremolo arm, for example simply by moving or changing the position of the guitar, causes pitch variation which is also not ideal.

The accuracy of any RTC mechanism is limited by design, manufacturing tolerances, materials, wear, cost, etc. These determine the accuracy and repeatability of their RTCs. The method of mitigating errors in RTC operation is in the "zero" region of the operating area, similar to "tilt" or tolerances within mechanical systems. The sensor method produces a range of values based on the position of the vibrato arm 20 and its central value (the "at rest" position) will be determined at the time of manufacture or calibration. In data processing software, it is a simple matter to allow a tolerance window (or zero region) such that the center position is not actually a single value, but a range of values around the actual center value.

According to the present embodiment, the "zero zone" is calculated from each direction (up or down) of the center position of the vibrato arm 20. Thus, the null region bi-directionally covers a particular offset from the center value. When the value read from the sensor is located within the zero zone, no pitch change is caused because the control unit sends a zero pitch change value to the pitch unit. This prevents the arm from being too sensitive to (unintended) user manipulation-even by gravity! And relaxing the absolute accuracy required of the RTC mechanism. This does not affect the high resolution available in the operating region outside the null region. In a preferred embodiment, the size of the null region is programmable. It is more useful because it defines a portion of the working area without ambiguity. It is highly repeatable and therefore a learnable aspect for the user.

This is shown in fig. 6. The figure schematically shows the vibrato arm 40 and its movement/rotation about the pivot point 41. The zero region is illustrated as shaded region 42. The size of the null region is exaggerated for clarity. In actual operation, a typical range for the null region may be +/-2 degrees. Of course, it will be appreciated that this is a matter of design choice in a particular embodiment. Arm movements within this area do not generate pitch change requests to the pitch processor. Instead, the control box 30 software sends a pitch request of zero, producing no pitch change, and ensuring that the instrument is at its reference pitch.

Fig. 9 shows software control of this process. The sensor values are read at 80. If the value is determined to be within the zero region parameter at 81, a zero pitch request is sent to pitch change device 36. That is, the arm is determined to be within a predetermined zero zone. In all other cases, the position of the arm is treated as normal at 83.

The addition of the zero zone reduces the absolute accuracy required for the RTC method of the mechanism. This reduces some of the burden placed on the mechanism, which in turn reduces cost and complexity. It may also prevent any jitter from the sensor system from being converted into an undesirably small pitch change by the subsequent pitch processor. In addition, it gives the user a small physical area of inactivity (pivoting of the arm). This is desirable in practice because it (a) makes it less likely that a malfunction will occur, and (b) enhances the tactile feedback when the user attempts to return to center.

However, the presence of the null region does change the linearity of the response to the vibrato arm motion. Before any pitch change begins, the user must move the arm out of the zero zone. If this null is too large, it is difficult for the user to perform a sensitive "wobble" near the center position-a common tremolo technique. As a result, there is an inherent conflict in the size of the null region, say manufacturing economy (larger) and the "feel" of the device to the user (smaller).

Even complex mechanisms designed to force the fixed central position have fundamental problems that cannot be completely eliminated: static resistance. This is a form of stiction, which is common in contacting objects. It prevents the vibrato arm 20 from returning to the central position accurately and with the desired accuracy.

In some cases, the force of the return spring may not completely overcome the stiction force that occurs when the arm is very close to its rest position. As known to those skilled in the art, stiction is for several reasons: electrostatic and/or van der waals forces and hydrogen bonding between them. This problem is likely to not occur in the case of a large force manipulation of the arm (due in part to the increased momentum of the arm due to the restoring force of the spring). However, when returning to the central position, the slow and gentle movement of the arms by the performer may cause them to reach a point of static resistance when in close proximity to the central position. The point at which stiction occurs will be the location where the dynamic and stiction of the spring return method are balanced. These forces are very small, so the errors that accompany returning to the center are also small, but not negligible. As previously mentioned, this will produce an undesirable pitch error.

The size of the null region is limited in two contradictory respects. Larger null areas make manufacturing easier, but smaller null areas provide better linearity for the player. A second strategy is taken to eliminate both these null zone conflicts and small errors caused by stiction, wear, etc.

This strategy will be referred to as edge zone (TZ) processing. A small null (e.g., +/-0.5 degrees) is defined and applied to the data from the sensor. This provides a limited version of the previously described benefits-immunity to jitter in "still" data, and reduces the required tolerances in the RTC mechanism. Nevertheless, this zero region is defined to be so small that it cannot accept errors like stiction, or to allow drift, wear or variations caused by temperature, gravity, etc.

Two other zones are established in the data adjacent to but outside the boundaries of the zero zone. The combined area of these regions may be arbitrarily large. For example, they may depend on inaccuracies or lack of repeatability of the RTC mechanism. These zones, nominally symmetrical around the zero zone, are labeled as edge zones (TZ). Which is depicted in fig. 7, TZ is expanded for clarity.

Fig. 7 shows a null 42 around the "true" center position of the vibrato arm 40. In addition, TZ 43 is defined on each side of the zero zone.

The software program in the control box 30 continuously checks the sensor values to see if they fall within TZ. Temporary history and heuristics are applied in this procedure to determine whether the TZ value is caused by the user or by errors in stiction, wear, etc.

An important factor to distinguish during TZ processing is whether the values from the sensors are mechanical "errors" (caused by stiction, for example) or the result of the player's music selection. These are very small errors in absolute terms around the "stationary" value, which is very important. However, small errors of magnitude in the performance in terms of instrument and other player "pitch" (in the "rest" position of the tremolo apparatus) are much larger than the musical meaning exhibited in absolute value.

In music, small changes in absolute pitch in the rest position are rarely selected as part of the performance. When used on music, small variations such as these are always small scale vibrato, i.e. small periodic variations in pitch around a reference pitch. The TZ process corresponding to this implementation is intended to distinguish between static errors and intentional periodic variations.

When the sensor values fall within the TZ zone, two key factors are analyzed:

(1) is the value constant (taking into account sample jitter) or varying?

(2) Is its duration longer than what is musically perceived if the value is constant?

If both analyses occur simultaneously (constant value, for a period of time), it is determined that this value is the result of a TZ error. The appropriate time period (for the TZ counter period) is partly subjective, partly empirical, and partly determined by inference, e.g. very few concerts change slowly, very small pitch changes. The most popular "western" music does not.

A rule of thumb (heuristic) is applied to determine the appropriate TZ counter period. For example, a small static pitch value around a "stationary" pitch may not last for a few seconds. However, a small static pitch value around a "stationary" pitch may last for several milliseconds. The latter may be an artistic choice or simply a mistake in the manipulation of the arm by the performer. The exact value may be determined by trial and error procedures and subjective preferences, but may be in the range of 0.05 to 1.0 seconds.

When the analysis program determines that an error has occurred, the software program remaps the original center value (determined at manufacture or by calibration) to a new calculated value. This value resets the center reference to a new value, thus setting a new null and TZ values around the new reference. In practice, the center value is not a fixed point, nor is it a predefined value or a value within a frequency band, but rather a sliding band of dynamically changing values.

The TZ process is enhanced (i.e., made less obtrusive) in operation by correcting errors using techniques such as successive approximation. This overcomes the step change in pitch which is apparent to the user if a (relatively) large correction is applied immediately. Alternatively, the program makes minor changes (e.g., an average of the difference between the previous center value and the current (incorrectly created) center value). Since the entire error analysis process occurs very fast (compared to human perception), a number of small corrections (e.g., successive approximations) can be performed, which are transparent to the user. In practice, this makes even (relatively) large corrections feasible.

Fig. 10 provides a flow chart illustrating an implementation of the TZ process. At 90, the new sensor values are read. If it is equal to the previous value, a small amount of jitter (a preset value) is added or subtracted, and the Z process begins at 92. Otherwise, this is an active movement of the arm, as usual at 94.

At 92, it is determined whether the value is within one of the TZ bands. If not, the value is passed at 93 for normal processing at 94. If so, the value is passed to the TZ counter at 94 and the counter is incremented at 96. And then passed to 97 where it is determined whether the TZ counter has overflowed. If not, then at 98, return to the top to obtain the new sensor value at 90.

If the value at 99 is yes, it is passed to process 100. The center value is reset to a value equal to the old center value plus the new center value divided by 2. A zero pitch change request is sent and the zero zone and TZ parameters are reset according to the new center value. The TZ counter is reset ready to enter the next cycle.

The advantages of edge zone processing are many: in the rest position, the vibrato mechanism is constantly and transparently corrected to zero pitch change (i.e., the instrument remains perfectly aligned with its reference pitch because the pitch processor does not inadvertently detune it)

TZ processing also provides the user with the benefit of maximum linearity of response and sensitivity in operation by minimizing the size of the null zone.

TZ processing also means that the RTC mechanism may be less complex while still providing acceptable performance and, if desired, may reduce manufacturing tolerances while still providing acceptable results. This in turn may allow for the use of lower cost materials and assembly processes.

Furthermore, various factors such as wear, direction with respect to gravity, temperature, movement during playing, etc. are constantly corrected without user intervention (i.e. recalibration), and it is also constantly corrected without player intervention during use of the device.

A third strategy employed in the current embodiment of the invention is to accommodate non-linearities in the algorithm to meet its desire to "feel" natural or intuitively feel comfortable with the pitch as the user moves the arm to generate a pitch change. Small pitch changes around the center position and near maximum and minimum arm deflections are requested to be readjusted so that the user can better control the device. This makes the tremolo effect easier to control (in a musical sense) when the user focuses his attention on (musically) important objects …, i.e. near zero pitch and maximum/minimum pitch variation. The non-linearity in the adjustment becomes particularly advantageous when the control unit is arranged to make large pitch changes at maximum/minimum arm deflections.

Fig. 11 illustrates a process for implementing this feature. At 100, a new sensor value is read, at 111, and a determination is made as to whether the value is near a critical point. If not, then at 112, the process proceeds to normal processing at 118. If so, at 113, the process 114 checks whether the user pitch preset is for a large pitch change. If not, at 116, the process proceeds to normal processing at 118. If so, at 115, the process 117 readjusts the sensor values to provide fine control (as described above). The rescaled values are then passed to process the pitch control normally at 118.

The fourth processing strategy makes the operation simple: a pitch change limit.

The pitch change "limit" is derived from the user switch settings and is implemented by firmware. In practice, these are user pitch presets. In practice, when the user moves the arm by a certain amount (e.g., 80% of its possible travel), the pitch change is frozen at a value determined by the user switch setting/pitch preset, regardless of further movement of the arm in the same direction. This has a strong application: the freeze value (or "limit") is predetermined (and therefore known) and it is guaranteed to musically coincide with the normal scale. This does not require user skill; this is an inherent function of the firmware. The musically appropriate limits can be set by the user in both directions (up and down) by using, for example, DIP switches connected to the processor, and in the present invention there are two "modes" a and B of operation, each with a selected pitch limit.

Fig. 12 shows a pitch presetting process in one embodiment. The sensor values are read at 120 and the software checks the state and mode of the DIP switch (or any other control mechanism used) to determine which pitch preset is active at 121. At 122, it is determined whether the pitch value corresponding to the sensor value is greater than the maximum allowable value or legal value in the mode. If not, then at 123, processing at 126 continues as usual. If it is larger, the process 125 freezes the pitch change at the maximum/minimum allowed value of the pattern at 124. Normal processing then continues and a new pitch value is requested at 126.

According to this embodiment, the operation mode is an optional foot switch: mode A is nominally a Bigsby/Strat style simulation, and mode B is nominally a Floyd Rose simulation. Most guitars will be familiar with these patterns. The user can immediately change the pattern to match the musical performance. The LED provides feedback of the current mode selection. However, it will be appreciated that more or fewer modes may be provided and controlled in any suitable manner.

A fifth processing enhancement according to this embodiment of the invention is arc mapping. All pitch changes can be adjusted over any size segment of the trill arm arc of rotation. For example, small pitch changes of (say) ± 1 semitone may be mapped to a full arc segment (for very fine control) or a small arc (for normal control). In the present invention, each pitch preset is mapped to a preferred span of the arc to provide the user with an intuitive operating area. This arc span mapping is part of the firmware process and is transparent to the user. In addition to intuitive operation, arc mapping has another useful attribute: to accommodate the physical layout of a particular instrument, it may be desirable to obtain, for example, maximum pitch, with the arm only rotating to 70% of its maximum travel. In this embodiment, each pitch is preset with a unique range of travel in each direction.

Fig. 13 shows an implementation of the arc mapping process. The sensor values are read at 130 and a determination is made at 131 as to which control switches and modes are active. Based on the preset, the maximum and minimum arcs are determined at 132 (e.g., based on a lookup table). The sensor values are then readjusted at 133 to obtain values within a predetermined arc preset for that pitch. This value is then sent for normal processing at 134.

The firmware has another mapping process (which follows the radian mapping) to re-scale the raw sensor data to the smaller data set required for MIDI 7 bit resolution. Due to the large amount of resolution of the sensor, a working operating range can be used within its large data set, while some can even be discarded, e.g. at maximum and minimum limits. This contributes to better manufacturing tolerances: not every sensor must be perfect. A system according to the described embodiments requires only a small data set from within a larger linear data set. This is advantageous in practice.

FIG. 15 provides an overall flow diagram of the various sensed pitch correlation processes and their interrelation. At 150, the new sensor values are read, and at 151 a pitch pattern is set based on the selection of the mode and input controls by the player.

Next, the zero region process 152 determines whether the value is in the zero region, and if so, the process reverts to reading the new value. Similarly, the TZ process operates at 155, and if the value is within TZ, the process reverts to reading the new value at 150.

If TZ and null are not applicable, then the value has any applicable non-linearity applied at 156, and the pitch change limit is checked at 157. The radian mapping is then applied at 158, the output is adjusted at 159, and a pitch change request is sent.

It is noted that the described embodiment is only one specific embodiment and that other embodiments, for example using different mechanical systems, may be used in combination with the electronic and software aspects of the developed method.

Unlike the mechanical trill method, the degree of movement of the arm need not have a fixed relationship to the degree of pitch change.

The degree of pitch change may be much greater than the physical system can tolerate-for example, it is not possible to use a mechanical crank to produce an up-pitch shift of an octave (12 semitones). The increase in string tension required for this pitch shift may break the string before the octave shift.

Virtualization of the vibrato system (which is ongoing with the process according to this embodiment) may provide functionality not previously possible to implement or experience in a mechanical vibrato system. One well-known problem that exists in virtualized devices is that people may have become accustomed to the physical system they are replacing. Thus, it is desirable that the virtual operating characteristics conform to human cognitive expectations-the virtual device must perform in a manner that humans can involve, predict, expect, etc. This is especially true in the sensitive control of pitch used to enhance musical expressions.

A complication in this requirement is that human perception is often very inconsistent with the current situation of what is happening in the real world. There is a very obvious small example of the human visual system: the eye is constantly moving (a form of shaking) to refresh the "data" presented to the retina. This movement is small in magnitude but within the acuity of human perception. However, it is completely hidden by the visual processing of the brain and therefore neither can be seen.

Preferred embodiments include software implemented strategies (e.g., non-linear and arc mapping) to alter the response to a user's striking motion, which in turn enhances the adaptation and "feel" of various operations. This greatly contributes to the ease of use of the device, particularly when performing pitch manipulation without physical precedent. These policies enhance the illusion that the virtual device is doing what you want, rather than the reality of what you are doing.

Take the range of the large pitch transition on the virtual percussion device as an example-for example, one octave up and two octaves down. This is a total of three octaves of pitch change-which is physically impossible. The degree of this pitch change will have to be propagated by arm movements/rotations, e.g. up and down 25 degrees. Simple calculations show that even small movements of the arm produce significant pitch changes.

This is obvious but not necessarily desirable. For example, one common function of a crank is "rock". This is a small, periodic pitch variation around the average pitch. This pitch variation is the most common type of vibrato heard on any instrument, including human voice.

When this large variation in pitch is mapped to a limited movement of the arm (in this example, ± 25 degrees), it becomes more difficult to achieve a satisfactory swing. It is difficult (especially with one-time excitement) to do so without moving the arm too much, which makes the pitch of the particular crank too large.

According to this embodiment, the software program solves this problem by a non-linear translation of the movement of the arm with respect to the pitch command sent to the pitch processor. The software process provides a change in the transformation (changing the "transfer function" of those skilled in the art) rather than the linear transformation required by the user's striking operation to provide a more intuitive response. This is illustrated by the previous case (large pitch change) example. For musical reasons, the rocking is usually at the end (or decay) of a phrase or note. Typically, when a phrase or note has reached its maximum pitch change (e.g., one octave) or no pitch change (i.e., the arm has returned to the middle).

Thus, when approaching either position-maximum pitch change or zero pitch change, it is desirable to "desensitize the arm". This is done by remapping the sensor data according to various sensitivity curves, each sensitivity curve being set for maximum pitch change and/or pitch change direction, up or down.

By having a specific sensitivity curve for each pitch change setting, the illusion of an "intuitive" response is greatly enhanced. The software according to the described embodiments transparently changes the linearity of its response to match the user's behavior to their natural expectations.

The present invention also provides a selectable mode of operation that effectively simulates the most successful mechanical variant, as long as the switch is lightly pressed (e.g., Bigsby, Stratocaster, Floyd Rose).

These well-known early mechanical products had unique pitch variation capabilities that were well known to those in the guitar world. The same pitch change setting that matches all of these products may be set on control box 30 (via the user-adjusted input switches described previously). Thus, the present embodiment mimics the characteristics of these earlier products, and can dynamically switch between simulations by using a mode footswitch.

The present embodiment produces pitch change data from its sensors/processes. In this implementation, the data is output in the MIDI format. These data can be used in other situations besides live performance. One of them is music recording. Keyboard/synthesizer players are now commonly used to record not only their performance audio, but also the MIDI data generated by their performance. The data represents aspects such as the note (i.e., pitch) played, its tempo, and sustain. By transmitting these data to another synthesizer having a MIDI function, it is possible to produce different tones or musical instrument sounds but with the musical characteristics of the original performance. MIDI data recording is already a common feature of most sound recording software.

This provides flexibility and convenience. Take a good performance record for example, but cannot be used due to a small error. It is often not possible to correct this error in the track (by editing, etc.) without which the sound is not audible. If the MIDI data of the performance is also recorded, the data can be corrected to eliminate the error. The data can now be fed to the original instrument which recreated the original performance. This can be re-recorded without any problems.

The concept of data recording may also be applied to pitch data produced by the present embodiment, and may be applied in a similar manner, for example: during the recording of the acquisition of MIDI pitch data and guitar sounds without pitch change. As known to those skilled in the art, this is very straightforward in most recording scenarios.

At a later date, the musician can correct any vibrato "errors" by changing/editing the MIDI data or re-recording any piece of data. The audio of the original performance is not affected or changed at all, and only the data driving the pitch changing device is affected or changed. Thus, this process is non-destructive and several rehearsals can be performed without the risk of losing the original performance.

Other possibilities are proposed: music pieces without vibrato operation may have the modification added after recording-again without losing the original performance.

Further, when the player finishes playing the musical instrument, a vibrato operation that is physically impossible to be achieved during the playing may be added later.

It is to be understood that the present invention includes various specific aspects, including mechanical, electrical, and software-implemented aspects. The invention includes these, alone and in various combinations with one or more of the mechanical, electrical or software aspects.

The mechanical systems described in relation to figures 3, 4 and 5 may also be used to control a purely mechanical vibrato arm. In this case, no magnet, sensor and PCB are required. However, these components would need to be made more robust and the torsion spring would need to have greater resilience to provide the necessary mechanical force. However, the principle of accurate RTC functionality still applies.

An implementation of such a mechanical embodiment is shown in fig. 17. A spindle 49 extends through the centre of the device with the arm mounting point 48 at one end. In contrast to the other embodiments described, the cams 47, 47A are separate with the main shaft 49 extending therebetween. This mechanical arrangement is otherwise similar to the previously described mechanism. A cam 47 engaged with collar 46, the return bias being provided by torsion spring 44; at the other end, cam 47A engages collar 46A, with return bias provided by torsion spring 44A.

The spindle 49 is also provided with sockets 57 along its length, wherein the sockets are spaced apart and spaced apart to receive the eyelets of guitar strings 55. Thus, rotation of the main shaft 49 will cause the tension on all the strings to increase, thereby producing a tremolo effect when played. The collar, cam and torsion spring arrangement will return the device accurately and allow a smooth playing action.

It will be appreciated that the present invention may be embodied in many different forms and used in conjunction with various features that are known and yet to be developed in connection with guitars and other musical instruments.