EP0258280A1 - Electronic stringed musical instrument - Google Patents
Electronic stringed musical instrumentInfo
- Publication number
- EP0258280A1 EP0258280A1 EP19870900668 EP87900668A EP0258280A1 EP 0258280 A1 EP0258280 A1 EP 0258280A1 EP 19870900668 EP19870900668 EP 19870900668 EP 87900668 A EP87900668 A EP 87900668A EP 0258280 A1 EP0258280 A1 EP 0258280A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- string
- strings
- coil
- instrument according
- trigger
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
- G10H3/00—Instruments in which the tones are generated by electromechanical means
- G10H3/12—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument
- G10H3/14—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument using mechanically actuated vibrators with pick-up means
- G10H3/18—Instruments in which the tones are generated by electromechanical means using mechanical resonant generators, e.g. strings or percussive instruments, the tones of which are picked up by electromechanical transducers, the electrical signals being further manipulated or amplified and subsequently converted to sound by a loudspeaker or equivalent instrument using mechanically actuated vibrators with pick-up means using a string, e.g. electric guitar
-
- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
- G10H2220/00—Input/output interfacing specifically adapted for electrophonic musical tools or instruments
- G10H2220/155—User input interfaces for electrophonic musical instruments
- G10H2220/165—User input interfaces for electrophonic musical instruments for string input, i.e. special characteristics in string composition or use for sensing purposes, e.g. causing the string to become its own sensor
- G10H2220/171—User input interfaces for electrophonic musical instruments for string input, i.e. special characteristics in string composition or use for sensing purposes, e.g. causing the string to become its own sensor using electrified strings, e.g. strings carrying coded or AC signals for transducing, sustain, fret length or fingering detection
Definitions
- This Invention relates to electronic musical instruments, and in particular with guitar-like instruments with improved means for detecting plucking of the strings.
- the invention is particularly suitable for use with the SYNTHAXE (Registered Trade Mark) instrument described in our International Patent Application Publication No. 084/04619 (United States Patent Application No. 691,486), to which reference should first be made for a detailed description of the background to this invention.
- That publication describes a guitar-like electronic musical instrument for use with a synthesizer.
- the instrument has a neck carrying six pitch strings which the player depresses onto conductive frets to determine the selected note, and a body carrying six trigger strings, separate from the pitch strings, which can be plucked or strummed to initiate or trigger the desired notes.
- the neck also includes coils embedded in the finger board which are designed to detect sideways movement of the pitch strings, a feature known as "string bending" often used by guitarists to vary slightly the quality and pitch of the note produced.
- the trigger or pluck detecting system described in publication 084/04619 detects triggers (plucks) by means of attaching each trigger (plucking) string to a magnet within a spring loaded barrel. As the string is tensioned, a mechanical counter- load is established within the spring, due to the increasing compression built up within the spring. When the string is released the magnet moves within the barrel, and a Hall effect device at the end of the barrel senses the movement of the magnet. Further analogue signal conditioning is applied to the raw signal thus generated to determine the velocity and the direction of movement (sense) of the magnet when it is released during a plucking action. Trigger signals (valid plucks) are defined according to the velocity of the magnet within the barrel.
- the string trigger design of our earlier publication was slightly unbalanced In being less insensitive to finger picking than to using a pick or plectrum.
- the sensitivity of the response fell off particularly when playing with plastic picks or plectrums.
- the lack of balance presented another assimilation problem to the guitar player.
- the system is also susceptible to external impacts on the instrument covers which could cause spurious notes to sound.
- the displacement signal such as from the Hall effect device, was also used to produce constant data relating to the absolute position of the string, as well as the velocity of the movement of the string.
- a valid trigger could be defined not just in terms of string movement velocity in a particular sense, but a further condition could be defined so that the string would have to return to its nominal mechanical zero point within a defined period of time.
- the principle object of the present invention is to remove peripheral mechanical attachments to the string and reduce the mass of the moving system to the minimum, which is the bare string alone. This permits the perceived relative sensitivity to different methods of plucking the string to be equalised, the string tension to be increased, and the energy imparted to the whole mechanical system to be less, hence reducing crosstalk to almost immeasurable levels and no susceptibility to extraneous knocks to the instrument covers.
- a further object is to faithfully determine string displacement and hence whilst a displacement exists to use subsequent electronic logic to inhibit the generation of trigger events unless the string was deliberately damped, thus satisfying the requirement to prevent unwanted triggers when a string was accidentally knocked.
- Another object is to reduce the complexity of the mechanical aspects of the design to reduce accordingly manufacturing costs.
- Figure 1 is a broken away perspective view of the mechanical part of a trigger detection system embodying the invention
- Figure 2 is a view of one of the coils
- Figure 3 is a block circuit diagram of the circuity connected to the coil outputs
- Figure 4 is a waveform diagram showing the coil output when there is a single simple trigger
- FIG. 5 is a similar diagram when there are three triggers in close succession
- Figure 6 is a similar diagram of a single trigger when the string is manually damped
- Figure 7 is a block diagram of the relevant part of the instrument circuitry based on Figure 24 of our earlier application;
- FIG 8 is a block diagram of processor A in the circuit of Figure 7;
- FIG. 9 is a block diagram of processor B in the circuit of Figure 7;
- Figure 10 is a view similar to Figure 1 of a modification of the trigger detection system
- Figure 11 shows the displacement transfer characteristic obtained from the coil in the modification of Figure 10.
- Figure 12 illustrates a typical waveform obtained from the coil of Figure 10 with the strings switched on cyclically each two cycles of the energising current.
- the example of the invention to be described comprises a string displacement transducing system that permits precise location measurement of an electrically conductive string that may form part of the playing system of an electronic stringed musical instrument.
- the improved trigger system illustrated is shown in Figure 1 as comprising a line of six coils 10 each beneath a respective one of six triggerable strings 12.
- One of the coils 10 is shown in more detail in Figure 2 and comprises a rectangular section silicon iron core 14 on which is mounted a bobbin 16 carrying a winding 18.
- the coil is positioned symmetrically under the string 10 with the longer axis of the rectangular core section parallel to the string. Thus the coils are in a plane adjacent and parallel to the plane containing the strings.
- the coils 10 are mounted on a printed circuit board 20 and located in an appropriate housing 22 in the body of the guitar-like instrument.
- the circuit board also includes suitable amplification circuitry.
- the trigger strings 12 are sequentially energised with an A.C. current in a similar manner to the string drive system used on the neck (pitch) strings in our earlier patent application.
- This A.C. string drive current induces a signal in the string trigger coil 10. Movements of the string in both the X and Y planes (i.e. laterally and at right angles to the fingerboard respectively) produce changes in the amplitude of the signal at the output of the coil.
- complex vibrations produce variations in the amplitude of the coil output signal, but when the string is at rest a steady output signal is generated by the coil. This steady state is used as a reference.
- a high frequency current of small amplitude is passed sequentially through each string, in the case of conventional guitars and guitar-style synthesiser controllers, there being six such strings as shown.
- the small pick-up coil is sited beneath each string relatively close to the bridge for the string set such that no impediment to free movement of string and/or player exists.
- the magnetic field emanating from the string is received in the coil and by a suitable amplification and phase-referenced detector method a bipolar signal that relates to the string position is obtained.
- This signal has been found to give very accurate positional information of the string in the plane of movement that is normal to the axis of the coil and Is moderately accurate in determining displacement along the axis of the coil.
- the output of the phase-referenced detector may in principle be utilised to produce the sound of the vibration of the string by further amplification, or may be processed further to determine If a trigger event has occured or if the string vibration has been subsequently damped by touching.
- the system includes a string current driver circuit 24 which applies current to the strings in a cyclical sequence through an electrical contact 26 associated with the physical string attachment point 28.
- the six coils are in this example connected to a multiplexer 30 which operates in synchronism with the string driver circuitry 24.
- the selected coil output Is applied to an analogue band-pass filter 32, and through a sample-and-hold circuit 34 which acts as a synchronous detector, to an analogue-to- digital converter 36. From there the signal is applied to processing circuitry of the type described in our earlier application (processor 2) which is adapted to undertake the necessary additional processing functions.
- processing circuitry of the type described in our earlier application (processor 2) which is adapted to undertake the necessary additional processing functions.
- the string driver circuit 24 can be constructed in a similar manner to the string drive circuitry used to apply current to the pitch strings for string bend detection purposes in our earlier application ( Figure 9 thereof).
- the system relies on the fact that when a current is passed through a thin straight conductor a circular, co-axial magnetic field exists around that conductor. If that current is oscillatory in nature, then the changing field will induce an emf into any adjacent conductor and a coil with many turns will particularly respond by generating a voltage at the output terminals. If the coil is placed with its axis normal to the string conductor, then a zero output is observed but as the conductor becomes displaced from that axis, then the output voltage will again increase but this time with a phase reversal. Thus a detector sampling the output waveform with a phase-sensitive ability will see bipolar changes of voltage to indicate the string distance away and which side it is situate.
- the energising current is produced from a constant current source to exclude variation in performance caused by production spread in electronic components and the use of different string types.
- One embodiment of the invention uses six small coils of approximately 1500 turns each of fine wire wound over a rectangular cross-section former fitted with the small flat, centrally placed soft iron core. This enables the six coils to be small enough for siting side by side beneath the trigger string set and sufficiently far removed to be fully encapsulated along with the small printed circuit board providing head-amplifica ion.
- the physical dimensions and shape of the coil coupled with the distance it is placed away from the energising string interelate closely and in a determined manner to assure maximum rate of change of output voltage as the string traverses its operating region coupled with good linearity.
- the energising current typically operates at approximately 50 kHz, being sufficiently high (e.g. above 20 kHz) to enable it to carry modulating information up to several kilohertz and be subjected to conventional filtering without loss of that information, and not so high as to create risk of either generating emissions or being susceptible to externally generated emissions. Its amplitude is typically of 10 to 20 mA.
- a microprocessor can be utilised to generate the high frequency waveform which is converted to triangular form which when communicated through loose coupling approximates to a square waveform. The microprocessor can then operate the current switching scheme for each string in turn and the appropriate switching of each pick-up coil to the main receiver amplifier and coordinate the activity of the sample and hold circuit followed by the analogue-to- digital conversion in a perfectly related manner.
- Figure 4 shows the output of one of the coils 10 when a simple trigger takes place. When the string is at rest, the trace is typically a straight line. Figure 4 shows a trace when the string is plucked. Note that in the moments while the string is being deflected, just prior to the moment of "pluck" when the displaced string is let go, the trace clearly shows the relative position of the string even before the string starts vibrating. This data is not available either on the string trigger system of our earlier application, or on a conventional electric guitar pickup.
- Figure 5 shows the coil output for a series of three triggers with the string being plucked in both senses, i.e. the third trigger is in the opposite sense. Here again the displacement effect is clearly seen.
- the system is microprocessor controlled and thus valid trigger definitions can be as subtle and sophisticated as the software engineer wishes.
- One possible sort of definition might be as follows.
- a trigger signal is defined as valid when the amplitude of the signal produced by the oscillations of the trigger string exceeds a predefined trigger threshold, and whose mean amplitude coincides with the steady state amplitude produced by a stationary string, plus or minus an operating window or tolerance.
- each string may now be set in software by altering the trigger threshold value.
- spurious triggers produced by overshooting fingers or picks are ignored. This is because, although an overshoot may produce a burst of oscillations, the string is mechanically offset by the overshooting finger or pick under these conditions, and the mean level of these oscillations will not coincide with the signal level of the steady state of the string.
- the system preferably does not re-arm itself to generate another trigger until the oscillations have fallen below a predefined re-arming threshold.
- This threshold is also adjustable as a value in software.
- the system is Inherently more sensitive and less frequency selective than the previous method. This is due to the fact that when the string is plucked, there is no mass to consider other than the mass of the string itself, and there are no frictional problems due to magnet barrels and housings etc. Also variations in string tension do not significantly alter the performance of the system, and the high tensions preferred by guitar players produce good, reliable results. Nevertheless, it may be possible to design the detection system to be even quicker in operation than that of our earlier application.
- Figures 7 to 9 of the present application illustrate the alterations required to implement the present invention.
- Figure 7 corresponds to Figure 24 of our earlier application to which reference is made for a description thereof, and shows that the analogue processor 3 is now divided into a processor A shown in Figure 8 and a processor B shown in Figure 9.
- the left hand touch sensing function of our earlier application can, in fact, be transferred into processor 1 and is not shown in Figures 8 and 9.
- Processor B outputs an inhibit command to processor 2 as shown for reasons discussed below.
- analogue signals from the transducers are converted to digital form in processor block 3 and then reconverted back to analogue form for onward passage to processor 2, processors A and B thus operating digitally.
- Figure 8 shows the steps of getting the "new string position' from a digital-to-analogue converter (DAC).
- the velocity is calculated by taking the difference between the new string position and the old string position.
- the peak, velocity is held in a peak hold circuit and this is emptied when the sign of the velocity changes (indicating the end of a velocity half-cycle). This continues cyclically with the peak velocity values being sent to Figure 9.
- the logical steps set out in Figure 8 are thus described by the following loop:
- Velocity new string position - old string position
- ABS absolute value (modulus).
- the processor block 3 has seven mode lines which are placed under control of processor 2. There are two modes per channel, inspect “on-velocity” and observe “off-velocity”. When “on- velocity” exceeds a given threshold, "note-on” events are initiated by processor 2 which then flips the mode line for that channel and peruses the "off-velocity” signal now being sent through instead. "Note-off” events are initiated by processor 2 when the separately acquired after-level signal reduces ostensibly to zero, implying that a trigger event is concluded. "Off-velocity" data is part of the “Note-off” signal protocol under MIDI (Musical Instrument Digital Interface standard) just as “on-velocity” is part of the "note-on” protocol.
- MIDI Musical Instrument Digital Interface standard
- processor 2 receives an inhibit signal from processor block 3 which is relayed to processor 1 and only allows processor 1 to carry out any neck switching operations when processor A is not acquiring a voltage from the trigger string coils, e.g. it is in the middle of a conversion from the sample/hold circuit when the desired voltage is already acquired and is then relatively immune to interference.
- the end result is the comprehensive control of the note triggering of a musical synthesiser.
- related systems can utilise the same transducing system to simultaneously acquire from the six strings of a conventionally strung and tuned guitar-style instrument by determining displacement behaviour the following:-
- FIG. 10 illustrates a modification of the arrangement of Figure 1 in which the six coils 10 under each trigger string 12 are all replaced by a single larger coil 40 extending across the width of all six strings. As well as needing less amplifiers, etc., this has the advantage of closer matching in performance between different strings, and also the ability to mount the coil 40 a substantial distance away from the strings. This makes it easier to house unobtrusively in the body of the instrument.
- the chief disadvantage is a certain susceptibility over smaller coils to extraneous electrical noise pick-up, particularly from the microprocessor systems in the instrument.
- a lesser disadvantage is the reduced output per string now available, which implies the need for extra amplification and/or offsets to optimise the dynamic range. Current returns for each energised string can be suitably placed to provide automatic offsets.
- Figure 11 illustrates the displacement transfer characteristic for such an arrangement
- Figure 12 shows typical waveforms obtained, assuming that the system cyclically switches between the strings so that each string receives two cycles of energisinig current from the string driver circuit 24. The sampled waveform is also shown.
Abstract
Des cordes à détente (12) d'un instrument de musique électronique en forme de guitare, sont situées à proximité de bobines transversales (10, 40) alimentées de manière cyclique en courant alternatif HF à partir d'une source (24). Les bobines émettent des signaux qui sont fonction des positions absolues des cordes, et non pas simplement de leurs vitesses, pour fournir une indication sûre de l'instant précis où une note doit être déclenchée par le pincement d'une corde.Detent strings (12) of an electronic musical instrument in the shape of a guitar are located near transverse coils (10, 40) supplied cyclically with HF alternating current from a source (24). The coils emit signals which are a function of the absolute positions of the strings, and not simply their speeds, to provide a reliable indication of the precise moment when a note should be triggered by the plucking of a string.
Description
Claims
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB868600417A GB8600417D0 (en) | 1986-01-09 | 1986-01-09 | Electronic musical instrument |
GB8600417 | 1986-01-09 | ||
GB8613748 | 1986-06-06 | ||
GB868613748A GB8613748D0 (en) | 1986-01-09 | 1986-06-06 | Musical instruments |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0258280A1 true EP0258280A1 (en) | 1988-03-09 |
Family
ID=26290189
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19870900668 Withdrawn EP0258280A1 (en) | 1986-01-09 | 1987-01-08 | Electronic stringed musical instrument |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0258280A1 (en) |
AU (1) | AU6845887A (en) |
GB (1) | GB2199686B (en) |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3902395A (en) * | 1973-10-11 | 1975-09-02 | William L Avant | Stringed musical instrument with electronic time division multiplexing circuitry |
US4321852A (en) * | 1979-12-19 | 1982-03-30 | Young Jr Leroy D | Stringed instrument synthesizer apparatus |
US4320681A (en) * | 1980-02-25 | 1982-03-23 | Dimarzio Musical Instrument Pickups, Inc. | Electromagnetic pickup device |
US4372187A (en) * | 1981-05-01 | 1983-02-08 | Ab Laboratories, A Limited Partnership | Novel guitar-like electronic musical instrument |
-
1987
- 1987-01-08 AU AU68458/87A patent/AU6845887A/en not_active Abandoned
- 1987-01-08 EP EP19870900668 patent/EP0258280A1/en not_active Withdrawn
- 1987-01-08 GB GB8720632A patent/GB2199686B/en not_active Expired - Lifetime
Non-Patent Citations (1)
Title |
---|
See references of WO8704288A2 * |
Also Published As
Publication number | Publication date |
---|---|
GB8720632D0 (en) | 1987-10-07 |
AU6845887A (en) | 1987-07-28 |
GB2199686A (en) | 1988-07-13 |
GB2199686B (en) | 1990-03-28 |
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Legal Events
Date | Code | Title | Description |
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PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
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AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT BE CH DE FR GB IT LI LU NL SE |
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STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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18D | Application deemed to be withdrawn |
Effective date: 19871012 |
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RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: AITKEN, WILLIAM, ALEXANDER Inventor name: SEDIVY, ANTHONY, JERRY Inventor name: DIXON, MICHAEL, STEPHEN |