GB2294158A - Switch assembly - Google Patents

Abstract

A switch assembly, for example serving as the fret switch in an hand-held musical instrument, includes an array of movable switch components 32 on a substrate 30. A much larger actuating plate 36 overlying each switch component is held against movement away from the switch component by a retaining means 34. A common cover layer 48 which is flexible enough to permit finger actuation of the actuating plates 36 extends over the retaining means 34. A playing transducer for the musical instrument comprises a resiliently mounted playing element (54, Fig. 5) providing first and second orthogonal playing surfaces (64, 66), one for actuation by a thumb and the other by a finger. A transducer element (62) is so arranged as to provide an electrical signal output on striking of either of the playing surfaces (64, 66). <IMAGE>

Description

MUSIC SYNTHESIZER This invention relates to music synthesizers and in one example to drum synthesizers.

Electric drum machines that imitate the sounds of a conventional drum kit (drums, cymbals, etc.) are well known. Pressure transducers are struck with drum sticks in a similar manner to the drums of a drum kit. Each transducer is associated by the user with a sound that imitates that produced by striking a particular drum or cymbal of a drum kit. These sounds are produced by, for example, the triggering of electronic voice generating circuits either situated within the machine or accessed through a communications interface such as MIDI.

A synthesizer with a different playing technique was disclosed in W086/01927. The disclosed synthesizer is portable and with the dimensions and shape of a guitar. It comprises two pressure transducers situated on the neck of the synthesizer for striking with the thumb and fingers of one hand. The outputs of these sensors are linked and connected via a buffer to an arrangement of analogue gates, each gate connected to the input of a different voice generating circuit. The gates are controlled by fret switches situated on the "fret board" of the synthesizer, so enabling different voice generating circuits to be triggered by striking the pressure sensors. With this instrument, therefore, the user associates each fret switch with one particular sound, selected by pressing the fret switch and triggered by striking one of the pressure sensors.

There is disclosed and claimed in a simultaneously filed patent application in the same name, music synthesizer apparatus for providing at an output, sound identification data and velocity data, the apparatus comprising a transducer adapted when struck in a playing rhythm to produce a signal output representative of velocity; selector means enabling selection by the player of one or more from a plurality of sounds and output means providing sound identification data determined by said selector means and velocity data determined by said transducer signal output; characterised in that there is provided threshold means producing an output through comparison of the transducer signal output with one or more preset thresholds, said output means being adapted additionally to provide sound identification data determined both by said selection means and by the output of said threshold means.

Advantageously, the threshold means serves to compare the transducer signal output with one or more preset velocity thresholds.

Suitably, the thresholds are adapted to be preset by the player.

The sound identification data, which according to the invention is controlled through either or both of the selector means and the threshold means, can take a variety of forms extending well beyond the conventional identification of MIDI note. Almost any item of MIDI information, including control information, can be included.

In this way, the player is offered a radically new way of selecting which sound is to be triggered by his striking of the playing transducer. The basic selection of sounds through fret switches or other selector means, still remains but - additionally - the player can set up his synthesizer apparatus so that a change to the velocity with which the playing transducer is struck, can change dramatically the characteristic of the sound produced, or even change the sound producing device which is being activated. With a drum synthesizer for example, a playing rhythm can contain (without the fret switches being touched), snare drum beats triggered by "softer" striking of the playing transducer and cymbal beats triggered by more vigorous striking.

It need not follow that the different sounds triggered above a particular velocity threshold, always have a higher reproduced velocity. The velocity range above the velocity threshold, can be mapped onto a different range.

Indeed, the velocity output from the pressure transducer may be in a different format from the velocity information eventually output from the apparatus.

It is one object of the present invention to provide improved fret switches for use with such, and indeed other, apparatus.

The design of fret switches for a playing instrument of this sort, should desirably meet a number of important - and sometimes conflicting criteria. A relatively large area of operation should be provided so as to accommodate slight inaccuracies in finger placement. The switches should have a pleasant "feel" and should react quickly and with minimum travel. It should be possible for the players fingers to slide easily from one to the next switch in the bank of fret switches. From a structural point of view, it is helpful if the switch assembly is of low depth. Ease and economy in manufacture are of course also important. Whilst maintaining robustness and resistance to wear.

It is accordingly an object of a further aspect of the present invention to provide an improved switch assembly for use with synthesizer apparatus or similar equipment.

Accordingly, the present invention consists in a further aspect in a switch assembly comprising a substrate; an array of switch components spaced on said substrate, each actuable by movement toward the substrate; an actuating plate overlying each switch component and of an areal dimension in the plane of the substrate substantially in excess of that of the switch component; retaining means limiting movement of each actuating plate in a direction away from the respective switch component and allowing generally free movement of the actuating plate toward the respective switch component and a common cover layer extending over the retaining means, the cover layer being flexible to permit finger actuation of the actuating plates through the cover layer.It is a further object of this invention to provide an improved playing pad or transducer offering reduced costs of manufacture and greater ease of construction than that previously disclosed.

Accordingly, the present invention consists in yet a further aspect in a playing transducer adapted for finger and thumb actuation comprising a housing; a unitary playing element mounted resiliently in the housing, the playing element providing first and second generally orthogonal playing surfaces; and a transducer element associated between the playing element and the housing so as to provide an electrical signal output on striking of either of said playing surfaces.

Preferably, the transducer element is disposed at around 45" to each of the orthogonal playing surfaces.

The present invention will now be described by way of examples with reference to the accompanying drawings in which: Figure 1 is a block diagram illustrating a circuit arrangement according to the prior art; Figure 2 is a front view of a music synthesizer according to the prior art; Figure 3 is a block diagram corresponding to Figure 1 but illustrating a circuit arrangement according to the present invention; Figure 4 is a sectional view through part of a switch arrangement according to the present invention; and Figure 5 is a sectional view through a playing pad according to a preferred form of this invention.

There is shown in Figure 1 the schematic arrangement of a portable drum synthesizer as disclosed in WO 86/01927.

The outputs from "thumb" and "finger" transducers 10a and 10b are taken in parallel to a bank of analogue gates 12 each controlled by a corresponding fret switch S, to Ss Actuation of a particular fret switch causes the transducer output to appear as the triggering input to a corresponding voice generating circuit V, to V5, the outputs of these circuits passing to a common output stage 14. In a modification discussed in WO86/01 927, remote voice generating circuits are used, via a communications interface such as MIDI. In that case, the blocks V, to V5 of Figure 1 can be regarded as MIDI note generators.

The portable drum synthesizer can desirably take the outward form of a guitar as shown in Figure 2. The fret switches S (of which there may be more than the five illustrated in Figure 1) are provided in the neck of the instrument. The transducer 10 takes the physical form of two separate transducer elements 10a and 10b disposed orthogonally, only one of these being visible in Figure 2.

For a more detailed discussed, reference is directed to WO 86/01927, the contents of which are to be regarded as incorporated within the present description.

Turning now to Figure 3, there is shown in a diagrammatic form similar to that of Figure 1, an arrangement according to the present invention. In this case, the output of playing pad or transducer 10 is taken first to a velocity decoder in the form of an A to D converter 22. The analogue playing pad creates an output voltage proportional to how hard it is struck. This output is converted into digital information by the velocity decoder 22. As with the prior arrangement, the transducer output is taken in parallel to a bank of gates, corresponding respectively with the fret switches S, to 5N The output of each gate is, however, connected to a velocity threshold detector 24. This compares the digitised transducer output, which is representative of how hard the playing pad was struck or, in musical terms, the velocity, with one or more thresholds.Depending upon the velocity level in comparison with these thresholds, a different MIDI note generator V11 to VtN is triggered.

In a context of a drum synthesizer, this enables the player to play a drum pattern involving a variety of drum sounds - and possibly a variety of devices creating different drum sounds - solely by controlling the velocity at which the playing pad is struck. This flexibility is of course additional to the selection facilities offered through the fret switches and therefore extends considerably the range of sound that can be triggered It is not essential that there is a one-to-one relationship between a particular MIDI note generator and a specific velocity range within one fret switch. In one important alternative arrangement a whole eight note cord could be assigned to one fret switch, with certain or all notes being audible or not, dependent upon the velocity of striking the playing pad.It will be understood that the arrangement of Figure 3 is a schematic representation and that the generation of particular MIDI notes can be handled by a single processor. The assigning of specific MIDI notes to particular fret switches and to particular velocity ranges within those fret switches can be controlled by the user through a suitable interface. The levels of the velocity thresholds can similarly be set by the user.

In a further modification, the sound information (usually in MIDI information) can vary as the threshold is passed not merely in the MIDI note but widely in form or in the MIDI channel which is addressed. Thus, by way of example, wholly different sound generation devices can be triggered above and below the threshold.

Typically, each channel in the synthesizer - corresponding to a particular selector means output - will have different user-defined threshold setting or settings.

Whilst it would usually be convenient to set threshold levels according to the velocity at which the playing pad is struck, there will be applications in which alternative types of threshold will be useful. Thus, for example, it will be possible to provide threshold means which serve to compare a particular sequence of pulses from the playing pad with a threshold actuation frequency. Beneath the threshold actuation frequency, the playing pulses will be coded as a first MIDI note whilst at higher actuating frequencies, a second MIDI note will be generated. Again, the change taking place at the threshold can be more widely in the form or channel of the MIDI information.

Whilst this invention has largely been described in the context of a portable drum synthesizer, it is not limited to portable instruments or indeed to drum synthesizers. The ability to select sound information by comparing velocity information from a transducer with velocity or other thresholds, will be of importance in a wide range of synthesizers including more conventional synthesizers. Indeed, the information taken from the transducer need not be "velocity" in the conventional musical sense.

The sound which is ultimately produced is of course not restricted to that of conventional musical instruments or indeed to conventional musical notes. Apparatus according to this invention could, for example, be used with great advantage in the triggering of sound samples.

In apparatus of this nature, the design of the selector means has a considerable influence upon the "playability" of the musical instrument. This is particularly the case where the apparatus takes the form of a portable instrument carried, for example, in the manner of a guitar.

There will now be described an improved fret arrangement according to the present invention which is believed to offer considerable advantage in terms of "playability". In addition, the fret switch arrangement has the important advantages of ease of construction and shallow depth. Where the fret switches are to be mounted in a relatively thin part of the instrument, such as the neck of a "guitar" a shallow depth is critical in ensuring that sufficient structural material remains such that the overall strength and robustness of the instrument is not diminished.

Turning now to Figure 4, there is shown a portion of a fret switch arrangement comprising a flat substrate 30. This can conveniently take the form of a printed circuit board carrying the necessary connection tracks for the switches. An array of perhaps eight switch components 32 (only one shown in Figure 3) are physically secured to the substrate 30 with the appropriate electrical connections to the tracks of the PCB. These switch components are of known form and are actuable by a relatively small movement toward the substrate. The switch components incorporate a degree of resilience and return to the rest position when the actuating force is removed.

A rectangular retaining wall 34 surrounds each switch component 32 and there is received within the cavity formed by the retaining wall, an actuating plate 36. This actuating plate has a planar lower surface 38 and an upper surface which includes a rim 40, an arcuate region 42 and a flat central region 44. The rim 40 of the actuating plate is trapped beneath an inwardly projecting lug 46 which is formed integrally with the retaining wall.

The assembly is completed by a cover layer or skin 48 which extends over the entire array. The skin 48 preferably takes the form of a selfadhesive label and adheres to the top surface 49 of the retaining wall and to the central region 44 of each actuating plate.

The actuating plate 36 is free to move toward the switch component, against the internal resilience of the component, so as to actuate the switch.

The skin 48 incorporates a sufficient degree of resilience to permit this movement. Optionally, the actuating plate is restrained against lateral movement by locating nipples 50 which extend laterally to engage the retaining wails. Movement of the actuating plate away from the switch component is limited by the lugs 46.

The described switch arrangement has a number of important features. Firstly, it is noted that the skin presents an entirely smooth upper surface enabling the player's fingers to slide freely from one switch to the next. Each actuating plate is considerably larger in dimension than the switch component which it operates so that the design is tolerant of small errors in finger placement.

A common problem in prior arrangements where an attempt has been made to provide a self-adhesive skin extending over a number of switches, is that, after minimal use, the label tears at the edge of the switch component. This problem is avoided in the described design. It will be noted, for example, that the curved region 42 of each actuating plate provides an area near the edge of the actuating plate where the skin is not bonded to either the retaining wail or to the actuating plate. The necessary extension of the skin or label can therefore be accommodated over a relatively large area, so reducing strain.

The manner in which the actuating plate is supported offers important advantages. If the plate is depressed from a central position, the switch is actuated with minimal degree of travel. If there is misalignment of the player's finger and the plate is actuated towards an edge, the plate will effectively pivot about the opposite edge. This means first that there is no upward movement of any part of the plate tending to lift the skin or label and, second, that a mechanical advantage is achieved in switch actuation.

Turning now to Figure 5, there is shown in cross-section the playing pad according to a preferred form of this invention. An L shaped recess 51 is formed at a corner of the main body part 52. A right-angled playing element 54 is resiliently mounted in this recess, for example by means of resilient support blocks 58. The playing element 54 may be formed of aiuminium or a suitably rigid plastics materiai. To the outside of the playing element 54, there is provided a cover layer 56 which is conveniently received at its ends, in shoulders 60 in the main body part.

A piezoelectric transducer element 62 is mounted at the apex of the playing element 54 and is disposed at 45" to each of the orthogonal playing surfaces 64 and 66 of the playing element. The transducer element is arranged to provide a voltage output determined by the strength with which the playing element is struck with a thumb on one playing surface or the fingers on the other playing surface. The equi-angular support of the transducer with respect to the two orthogonal surfaces provides for simple balancing of the playing pad response to finger and thumb actuation respectively. It has been found in the past that the balancing of a separate "finger" transducer with a separate "thumb" transducer can present difficulties.If desired, the transducer can be offset slightly from the 45" angle to compensate for the slight tendency, with a typical player, of striking harder with the thumb than with the fingers.

The piezoelectric element can take a variety of forms, one example being shown in Figure 5 with the scale exaggerated for the purposes of clarity. Thus, the piezoelectric crystal 70 is mounted on one side of the 45" element, the opposing face of the crystal then carrying a counter-weight 72.

It is found experimentally that, even with a relatively small counter-weight, sufficient inertia is provided for movement of the playing pad to be adequately transduced to a voltage output. In an alternative arrangement, the piezoelectric crystal is supported between the 45" element and the main body part of the apparatus. This is anticipated to produce a larger signal output but is less convenient in manufacturing terms.

It will be understood that the described arrangements are but examples of a wide variety of ways in which a single transducer element can be disposed to provide a balanced response to striking of two generally orthogonal services of the playing element. Electromagnetic or magnetostrictive transducers could be employed; strain gauge technology would provide an alternative.

Claims (6)

1. Switch assembly comprising a substrate; an array of switch components spaced on said substrate, each actuable by movement toward the substrate; an actuating plate overlying each switch component and of an areal dimension in the plane of the substrate substantiaily in excess of that of the switch component; retaining means limiting movement of each actuating plate in a direction away from the respective switch component and allowing generally free movement of the actuating plate toward the respective switch component and a common cover layer extending over the retaining means, the cover layer being flexible to permit finger actuation of the actuating plates through the cover layer.

2. Switch assembly according to Claim 1, wherein said retaining means comprises a lip engaging at least a portion of the margin of the associated actuating plate.

3. Switch assembly according to Claim 2, wherein upon finger actuation of the actuating plate toward one region of the margin, the actuating plate is adapted to pivot about the engagement with said lip of an opposing region of the margin.

4. Playing transducer adapted for finger and thumb actuation comprising a housing; a unitary playing element mounted resiliently in the housing, the playing element providing first and second generally orthogonal playing surfaces; and a transducer element associated between the playing element and the housing so as to provide an electrical signal output on striking of either of said playing surfaces.

5. Transducer according to Claim 4, wherein the transducer element is disposed at around 45" to each of the orthogonal playing surfaces.

6. Transducer according to Claim 4 or Claim 5, wherein the transducer element comprises a piezo-electric element.