US3445579A - Electronic musical apparatus - Google Patents

Description

y 20, 1969 J. MARKOWITZ ET AL 3,445,579

ELECTRONI (I MUS I CAL APPARATUS Filed Feb. 8, 1965 Sheet INVENTO/PS. JEROME MARKOW/TZ ERHOLD ER/POL ROBERT GRIFFITH JAMES R/CHARD WETH 19V 70 PREAMI? ATTORNEYS.

J. 'MARKOWITZ ET AL 3,445,579

ELECTRONIC MUS I CAL APPARATUS Sheet. & of 3 May 20, 1969 Filed Feb. 8, 1965 INVENTO/PS. JEROME MAR/(OM07? [IV/POL R08E/P7' GRIFFITH JAMES RICHARD WETHERHOLD ATWRNEKS'.

20, 1969 J. MARKOWITZ ET AL 3, 5,579

ELECTRONIC MUSICAL APPARATUS Sheet Filed Feb. 8, 1965 w o w WW 6/ T If m a mu: 51m!- RR A A H Mum m mm: RRM ERA JEJ B 2 H ED 0 m ATTORNEYS.

United States Patent 3,445,579 ELECTRONIC MUSICAL APPARATUS Jerome Markowitz, Allentown, Errol Robert Grilfith,

Topton, and James Richard Wetherhold, East Texas, Pa. (all Allen Organ Company, Macungie, Pa. 18062) Continuation-impart of application Ser. No. 275,380,

Apr. 24, 1963. This application Feb. 8, 1965, Ser.

Int. Cl. Gh 1/02, 3/00; G10c 3/06 US. Cl. 84--1.24 13 Claims ABSTRACT OF THE DISCLOSURE An electronic musical instrument having a keyboard and piano action transduces the action movement into a musical tone, preferably having the tonal qualities of a piano. Electronic and acoustical components are used to produce musical tones without the aid of strings or a conventional sounding boar-d. A knock sound generating device is included to duplicate the knock sound typical of conventional pianos.

In general, this invention relates to a new and improved electronic musical apparatus utilizing electronic and acoustical techniques for producing the sound of aconventional piano and/or organ. More particularly, it is directed to an electronic piano which may be utilized with any of the known piano actions with the same degree of control as presently possible with conventional pianos.

This application is a continuation-in-part of application Ser. No. 275,380 for Electronic Musical Apparatus, filed Apr. 24, 1963 now United States Patent 3,248,470.

The conventional piano produces its characteristic tone by an action consisting primarily of mechanical levers by means of which a felt hammer can be caused to strike one or more taut steel strings with a wide range of velocity and force causing the strings to vibrate. These vibrations are transmitted to a sounding board for amplification. An extremely high order of control can be exerted on the amplitude and other tonal characteristics of the sound by a skilled performer. The wide range of amplitude results mainly from the construction of the mechanical linkage between the key which is struck by the performer and felt hammer.

In the past, electrification of pianos has fallen along certain conventional lines. That is, developments in the past have been directed to the electrical amplification of the sound produced by a piano. These techniques included utilizing the strings to excite electromagnetic or electrostatic pick-ups, or by having the hammer strike vibrating reeds which produced output signals in accordance with the mode of their vibration. However, these techniques produced pale imitations of the sound produced by a conventional piano and were therefore not acceptable except as novelty items.

In accordance with the teachings of the present invention, an electronic piano is disclosed which utilizes a conventional piano action, plus electronic means for producing an electrical signal which when amplified and transduced by a suitable speaker will produce a piano-type tone. A piano constructed with the electronic means of the present invention resembles a conventional piano in respect to the keyboard and key action, but the strings and conventional sounding board are replaced by electronic and acoustical components.

In accordance with the present invention, the electronic means is operative from the felt hammer of the piano action to produce a signal in acordance with the velocity of the hammer. This is similar to the operation of the strings 3,445,579 Patented May 20, 1969 of a conventional piano. Each note on the piano scale is produced electronically with its amplitude dependent upon the force and velocity of the hammer.

It has been recognized that the tonal characteristics of a piano are a combination of many factors including the vibration of the string. Among these factors that make up the basic tonal characteristics of a piano is the knock which occurs the beginning of every note'when a piano strings. However, in an electronic piano of the type disby the impact sound of the hammer against the strings which is transmitted and in effect amplified by the sounding board. It is one of the objects of the present invention to provide an electronic piano which acoustically reproduces the knock effect.

One step in adjusting the action of a conventional piano involves the realignment of the shank and hammer with the strings. This is normally acomplished by simple observation of the hammer through the spacing between strings. However, in an electronic piano of the type disclosed herein such observation is not readily made. Accordingly, it is an object of the present invention to provide a means whereby the magnetic core mounted on the action hammer may be properly aligned with the transducer coil.

In the construction of an electronic piano, it has been found that the coils used for transducing the piano action into an electronic signal have a transformer action caused by their close juxtaposition. This transformer action may result in the production of unwanted notes. It therefore is an object of the present invention to provide a novel means for isolating the coils to avoid the foregoing described problem.

Electronic pianos constructed in accordance with the present invention use magnets mounted upon the action hammers. As in conventional pianos, these hammers are mounted in close side-by-side relationship. The magnets are in such close proximity that movement of the magnet when the action key is struck causes adjacent magnets and hammers to move slightly. This movement may result in the production of unwanted noise and a lowering of the efiiciency of the action. Accordingly, it is another object of the present invention to provide a magnetic barrier for isolating the magnets from one another to avoid movement of adjacent action hammers.

It has been determined that the construction of an electronic piano must take into account factors other than the production of the musical note. For example, it is also necessary to take into consideration the effect of the instrument upon the player. This may be referred to as a psycho-acoustic effect. In a conventional piano the psychoacoustic effect manifests itself in the transference of vibrations from the sounding board back into the piano keys. The player feels these vibrations in his fingers and it could affect his playing when it is not present. It therefore is still another object of the present invention to provide a means whereby the vibration caused by the generation of sound is transferred back into the piano keys where it may be felt by the player.

Therefore, it is a general object of this invention to avoidthe foregoing and other difficulties of the prior art and to achieve the results discussed above by a provision of a new and improved piano utilizing electronic tone generating techniques.

A further object of this invention is the provision of a new and improved electronic piano capable of producing musical tones directly from the piano action by electronic components substituted for the standard strings and sounding board.

A still further object of this invention is the provision of a new and better electronic piano which utilizes a velocity sensitive transducer operative from the felt hammer of a piano action to produce a piano-type tone normally associated with the particular key being struck.

Another object of this invention is to produce a new, better and lighter weight piano which incorporates all of the features of tone variation possible in conventional pianos.

Still another object of the present is the provision of a new and better piano which requires tuning only at infrequent intervals by utilization of electronic sound producing components.

Yet another object of this invention is to provide an electronic tone generator capable of producing a pianotype tone in response to a velocity sensitive key action and/or to produce an organ-like sound of sustained amplitude when operated from an organ-type key contact arrangement.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there are shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a perspective view of an electronic piano with a portion thereof cut away to show the knock producing apparatus.

FIGURE 2 is a bottom plan view of the piano shown in FIGURE 1.

FIGURE 3 is a side view of a piano action incorporated in the instrument shown in FIGURE 1.

FIGURE 4 is a top plan view of the transducing coils for the musical instrument taken along the line 4--4 of FIGURE 3.

FIGURE 5 is a partial top plan view of the piano action shown in FIGURE 3 taken along the line 55.

FIGURE 6 is a sectional view of a transducer coil taken along the line 6-6 in FIGURE 3.

FIGURE 7 is a schematic showing the electronic means for producing the piano tone associated with the action of FIGURE 3.

FIGURE 8 is an alternate embodiment showing the electronic means for producing the piano tone associated with the action of FIGURE 3 and an electronic knock producing circuit.

Referring now to the drawings in detail, wherein like numerals indicate like elements, there is shown in FIG- URE 1 a perspective view of the electronic piano and/ or organ of the present invention designated generally as 10. The electronic piano is shown mounted in the case of a conventional grand piano.

As shown, the piano 10 includes a keyboard 12, and pedals 14. The keyboard 12 consists of a plurality of keys 16 mounted in conventional side-by-side relation.

One of such keys 16 and its action 18 is shown in FIG- URE 3. The action 18 is of the type which may be used in a grand piano.

The action 18 includes a key 16 mounted on a key frame 20 for pivotal movement about a balance rail 22. The balance rail 22 has an upstanding balance key pin 24 extending through a hole provided in the key 16. The key frame 20 has a pair of cushions 26 and 28 associated with each end of the key 16 to insure a smooth limit stop for the movement of the key 16. The piano action 18 is intended to transmit pivotal movement of the key 16 into upward movement of the hammer 30 which is attached to a suitable hammer shank 32. The hammer shank 32 is pivotally secured at the pivot point 34 to the hammer butt 36. The hammer butt 36 is mounted on the frame 38 by means of a pin 40 which threadedly engages the frame 38. The pin 40 may be loosened to adjust the angular position of hammer 30.

The hammer shank 32 rests on a hammer rest 41. The hammer shank 32 has a hammer shank roller 42 associated therewith resting on a suitable jack or grand fiy 44.

The key 16 has a capstan screw 46 integral therewith and utilized to transmit rotative movement to a suitable wippen 48 pivoted about the frame 38. The jack 44 is pivoted about the other end of the wippen 48 so that upward movement of the screw 46 causes the jack 44 to force the roller 42 of the hammer shank 32 upwardly to provide upward movement of the hammer 30. The jack 44 is guided in this movement by an escapement lever 50 pivotally mounted about a top flange of the wippen 48. The jack 44 is further returned to its initial position by a suitable repetition spring 52 and the escapement lever 50 is returned to its initial position by a repetition spring 54 to thus aid in biasing the key 16 to its released position shown in FIGURE 3.

The key 16 has a hammer check 56 mounted at the end thereof to cushion the return of the hammer 30 after the completion of a stroke.

All the elements discussed above form a portion of the grand piano action 18 and are conventional. Any type of piano action, such as an upright action, could be utilized in place of the grand piano action 18.

The hammer 30 has at its striking end a cushion 58 surrounding a magnet 60. The magnet 60 is adapted to enter a suitable opening 62 in a coil 64 mounted above the hammer 30. The opening 62 is best shown in FIGURES 4 and 6. When the key 16 struck by the player, the coil 64 acts as a transducer for the electric piano tone generator 66 associated with the particular piano action 18 discussed previously. The coil 64 transduces the movement of the magnet 60 on hammer 30 directly into an electric pulse proportional to the velocity thereof.

As stated earlier, the importance of the piano rests upon its powerful and finely and graduated tone and its convenience for the production of concerted music. Thus, the electronic piano tone generator 66 must be capable of utilization with a piano action of the general type to control one or more electronic oscillators. Further, means must be included in the piano generator to control the amplitude, decay characteristic, and the pulse length of the oscillator to vary the tones produced thereby.

The circuitry forming the piano tone generator 66 may utilize two separate generating circuits which are utilized to stimulate the sound generating from a two-string tone. In a conventional piano, the strings are steel wires of graduated thickness and length, the larger being made heavier by being wound with copper wire. For each of the extreme lower tones, only one wire is provided, but for most others, there are two or three wires which are tuned in unison and placed so that they will be simultaneously struck by a single hammer. The tone generator 66 is associated with a key adapted to produce one of the middle notes on the piano scale utilizing two strings struck in unison.

The components of the circuit 66 will be discussed in an integrated discussion of their operation. Certain of the elements drawn in full detail in other figures are shown schematically in FIGURE 7. However, to simplify understanding of the invention they have been assigned like numerals.

The coil 64- has one terminal connected to a source of supply Eb and its other terminal to the base terminals 68 and 168 of transistors 70 and 72 respectively. The magnet 60 is a permanent magnet attached to the hammer 30 which will enter the coil 64 with a velocity that will be proportional to the velocity with which the key 16 is struck. Since the induced voltage in a coil is determined by the number of flux lines cut per unit time, the voltage developed across the coil 64 will be proportional to the velocity of the struck piano key within limits.

The coil 64 voltage is applied between the base 68 and emitter 74 of transistor 70 causing it to conduct and resulting in the charging of capacitor 76 from the source Eb. The charge on capacitor 76 causes the transistor 78 to conduct and, in so doing, applies the voltage Eb to a Hartley oscillator 80. The oscillator 80 includes a transistor 82 having a split inductance 84 utilized to tune the collector circuit of the transistor 82.

The conductivity of transistor 7 8 varies with the charge on capacitor 76 or, in other words, with the voltage induced in the coil 64. The oscillator 80 operates in a manner whereby the output will be a sound wave whose amplitude will be approximately proportional to the input voltage. The output of the Hartley oscillator 80 is applied through a wave shaping circuit 85 to the audio output and loudspeaker means 86. The wave shaping circuit 85 is a standard means of imparting a string quality on the amplified and transduced sound.

In a conventional piano, there is normally provided a damper which will damp the string after the key is returned to its initial position. This damping is achieved in the piano tone generator 66 of the present invention by utilizing a switch 88 located below the key 16. The contacts 88 are opened when the key is struck and closed when the key is in its normal position. After a key is struck and the capacitor 76 has charged as discussed previously, it discharges through a high resistance resistor 90 and transistor 78 so that it has a long time delay as would be normal when striking an undamped key on a piano. However, when the key is released and returns to its up or closed position, the capacitor 76 can discharge through diode 92, low resistance resistor 94, and the nowclosed contacts of switch 88 to ground. The capacitor 76 voltage will thus be quickly reduced to zero voltage and the oscillator 80 will cease to oscillate.

A second switch 96 is connected in series with the switch 88 and every other switch 88 associated with each key of a piano to perform the function of the sustaining pedal on the piano. The sustaining pedal on a conventional piano prevents the dampers associated with every key from dampening the vibration of their associated keys. The sustaining switch 96 performs its function by allowing the voltage on capacitor 76 to continue to decay through the resistor 90 and transistor 78 by opening the circuit between resistor 94 and ground. The switch 96 may be operated by the pedals 14 shown in FIG. 1. The tone produced by striking the key 16 will decay for a period of time after the key has been released in the same manner as a conventional piano whose sustaining pedal has been depressed.

The portion 98 of the tone generator 66 has substantially the same components as the portion 61, as it is merely intended to reproduce a string exactly similar to the string reproduced by the portion 61 in the same manner as a two string tone on a conventional piano. The portion 98 will be controlled in the same manner and simultaneously with the portion 61, and will provide the additional amplitude plus any possible interference effects which result from slight differences between the two identical circuits. The portion 98 has been noted with numerals exactly one hundred more than its associated components in portion 61. For example, the oscillator 180 is similar to the oscillator 80 discussed previously.

In a complete piano built in accordance with the principles of the present invention, each key will be associated with a similar set of components as described heretofore, but tuned to the required frequency. The sustaining contacts of switch 96 would connect to a common bus 200 associated with all the contacts similar to the contacts of switch 88. Isolating diodes would be provided between each key to prevent interaction of the oscillators.

As indicated above, the mechanical arrangement may be provided so that the contacts of switch 96 would be actuated by the foot pedal 14. Further, the piano could be designed to prevent a separate pedal which would sustain only the bass notes rather than all of the notes. Additionally, a sostenuto pedal could insure the sustaining of a tone after the particular key had been struck. Still further, a soft pedal could be provided to act as an electronic substitute for the conventional soft pedal by switching out one portion of each tone generator having more than one oscillator. This would lessen the amplitude of the output signal of the tone generators in the same manner as is now done on conventional pianos. In the alternative, the

soft pedal could proportionately lessen the amplitude of the output signals of the tone generator.

The tone generator 66 can additionally be utilized with a separate set of organ keys for producing an organ-like sound of sustained amplitude either separately or in combination With the piano discussed above. The organ keyboard has been shown representatively by the organ key 98. The organ key 98 rotates about a fulcrum 100 to open and close associated contacts 110. They key 98 is spring-loaded to an open position by a conductive spring 112 connected to the source voltage Eb. Upon pressing the key 98, contacts are closed completing a circuit from the voltage source Eb through a resistor 114, capacitor 116 and wave shaping circuit through the input of transistor 182 in oscillator 180.

In the interest of economy, the organ contacts could be placed below the piano key 16 and suitable switches arranged in a circuit to cut out the piano signal transducer as well as connecting the organ contact to the oscillator and vice versa.

As shown in FIGURE 1, the keys 16 are arranged in side-by-side relation. Accordingly, the actions 18 and coils 64, associated with each key are also arranged in side-by-side relation. This is best illustrated in FIGURES 4 and 5. In FIGURE 4, the coils 64 for the respective hammers are shown. In FIGURE 5, the hammer shanks 32 are shown pivotally connected to the adjustable hammer butts 36 on frame 38. As has been indicated previously, the close juxtaposition of the actions 18 and coils 64 may create problems of inductive and magnetic coupling. Moreover, the nature of the coil structure and its mount to be described make it difficult to adjust the angular position of hammer butts 36 and hammers 30 so that magnets are properly aligned with openings 62. The novel solution to these problems will be set forth in the following detailed description of coils 64 and their mounts.

The coils 64 are supported above the hammers 30 by means of upright brackets 120, one of which is shown in FIGURE 3. The brackets support a pair of transverse rails 122 and 124 which extend across the actions 18. Each coil 64 depends from a plate 126 above its associated hammer 30. The coils 64 and plates 126 are positioned on the rails 122 and 124 so that the magnet 60 will enter opening 62 when key 16 is struck.

Coil 64 is tightly held against plate 126 by means of a pair of threaded fasteners 128 and 130. The fasteners 128 and 130 may be made of a non-magnetic material to avoid interference with the magnetic properties of coil 64. The plate 126 is rigidly fastened on rails 122 and 124 by means of a pair of threaded fasteners 132 and 134.

As indicated above, a step in adjusting the action of the musical apparatus 10 is to adjust the alignment between hammer 30 and opening 62 in coil 64 by means of pin 40. Since the hammers are below the coils 64 which are positioned close together, it is difficult to see the magnets 60 to properly align them with openings 62. In order to overcome this problem, the plates 126 are made of a transparent plastic material such as Lucite. By providing this transparent material, it is made possible to observe the magnets 60 while aligning them with openings 62.

As best shown in FIGURE 4, the coils 64 are closely spaced together. As a consequence of this close spacing, it has been found that when a pulse is generated in one of the coils 64 it is inductively coupled to an adjacent coil. The inductive coupling may be suflicient to generate a voltage pulse which will initate an unwanted tone. To prevent inductive coupling of sufficient magnitude to cause generation of unwanted tones, each of the coils 64 is wrapped with an outer layer of a nickel-iron alloy having high permeability, particularly at low flux densities. Nickel-iron alloys having these characteristics are known as permalloy, hipernik, supermalloy, and mu-metal. This has the property of isolating the coils 64 so as to prevent inductive coupling.

As is the case with the coils 64, the hammers 30 and their magnets 60 are spaced apart by short distances with the result that individual magnets 60 tend to interact with each other. This interaction manifests itself in two ways. First, the upward movement of a magnet 60 tends to pull adjacent magnets a short distance upwardly. This movement is transferred back into the keys and is apparent on the keyboard. As a consequence, it may seriously aifect the ability to play successive adjacent notes. To avoid this problem, a magnetic shield 138 extends between brackets 120 behind the hammers 30. The magnetic shield 138 is curved so that it may be positioned as close as possible to the magnets 60 without interfering with the movement of hammer 30. The magnetic shield 138 is made of a magnetic material such as iron or steel. It effectively breaks up the magnetic field extending around each individual magnet so as to reduce magnetic interaction. Accordingly the striking of one key 16 and movement of its associated hammer 30 and magnet 60 has no effect on adjacent keys, hammers and magnets.

As has been indicated previously, it is desirable to pro vide an electronic piano with the tonal characteristics of a conventional piano known as knock. This can be accomplished acoustically in the following manner. A sound conducting rod 140 is fixedly mounted to one of the rails 122 and 124 that support plates 126 and coils 64. When the key 16 is struck, hammer 30 impacts the cushion 58 against coil 64, causing, in addition to the electronic pulse, a single acoustic pulse of energy. This energy is normally of such a nature that it would hardly be heard except that it is transmitted through acoustic conducting rod 140 into a sounding board 142 fixedly mounted on top of rod 140. Although the sounding board 142 is shown as a box-like structure having its bottom side open, it may take any one of several configurations. For example, it would be a board or a tuned cavity. The sounding board 142 is preferably made from long grained wood such as spruce. The sounding board 142 is constructed in accordance with principles known to those skilled in the art.

The sound board couples the acoustic energy pulse to air, which in turn radiates it in the same manner that a normal sounding board of a piano would radiate such energy. Since this is a pulsing device, striking any given key, plurality of keys or sequential series of keys will result in a collective burst of sound substantially the same as that which occurs in a piano.

Although it is possible to use a single sounding board 142 coupled through the rail 124 and rod 140 to each of the coils 64, it has been found that a better result can be achieved by using three boards. The strings of the conventional piano are normally divided into three groups. These may be classed as high notes, middle notes, and low notes. The sounding board of a piano is effectively divided into three sections. The smallest section is coupled to the highest notes and the remaining two sections become progressively larger as the lower notes are approached. By of notes, a somewhat smaller board to the middle section coupling a large sounding board 142 to the lowest section of the electronic piano, and a still smaller board to the highest notes, the pitch of the knock will be varied in the same manner which occurs in a conventional piano. This is illustrated in FIGURE 1 wherein a second board 142' is shown coupled to the middle section notes.

In the alternative, knock may be produced electronically. An electronic circuit for so producing knock is shown in FIGURE 8. The coil 64 has one terminal conneoted to the primary side of a coupling transformer 144. Its other terminal is connected to the opposite side of the transformer primary through potentiometer resistance 146. The magnet 60 mounted on hammer 30 is illustrated schematically by means of an arrow. The transformer 144 couples the voltage pulse generated by the movable magnet 60 to the base of transistor 148 through resistor 150. When the voltage pulse generated in coil 64 is applied to the base of transistor 148 it is caused to conducct, resulting in the charging of the capacitor 152. The charge on capacitor 152 causes the transistors 154 and 156 to conduct and is doing so applies the voltage source E through a Hartley oscillator and wave shaping circuit (not shown). The Hartley oscillator and wave shaping circuit may be of a type similar to that shown in FIGURE 7. It should be apparent that the operation of the circuit shown in FIGURE 8 as thus far described is similar to that shown in FIGURE 7.

In order to generate a knock sound, the voltage pulse generated in coil 64 is coupled through potentiometer 146 and matching transformer 158 to a tuned filter consisting of capacitors 210 and 212 and inductor 214. The tuned filter is tuned to a frequency approximating that of the knock sound. This frequency is connected to a preamplifier and amplifier which amplify the sound and apply it to a transducing means such as a loudspeaker. In this manner, the knock sound may be electronically reproduced.

As has been previously described with respect to the circuit shown in FIGURE 7, the tone generating circuit may be provided with a circuit to selectively damp or sustain the generated signal. The damping circuit is illustrated by the resistor 90, diode 92 and switches 88 and 96. These circuit elements operate in the same manner described with respect to the circuit shown in FIGURE 7 and hence need not be further explained.

The creation of the psycho-acoustic effect wherein vibrations are transferred back to the fingers of a player throughkeys 16 in an electronic piano is accomplished as follows. A tuned cavity consisting of a box-like structure 218 is mounted on the bottom of the piano case. Tuned cavity 218 may be made of a long grain wood such as spruce and has its open side mounted adjacent the bottom of the piano case. The speakers 86 are mounted in the bottom or closed side of cavity 218 so that they broadcast into the cavity. Although four speakers are shown, it will be understood by those skilled in the art that the number of speakers may be varied in accordance with the size of the piano and type of tone desired.

The tones broadcast into cavity 218 reflect off the bottom of the piano case. As a result, a certain portion of their energy is transferred into the Case and transmitted to the key frame 20 and keys 16 in much the same manner that a conventional piano soundboard transmits sound energy to the piano keys.

The tuned cavity 218 also serves another purpose. That is, it serves to amplify the sound generated by speakers 86. The amount of sound amplification is a direct function of the size and shape of cavity 218. Thus, by varying the size and shape of cavity 218 it is possible to vary the overall sound of the piano. One distinct advantage of this is that by using the same electronic equipment and speakers, and merely varying the size and shape of the tuned cavity 218, it is possible to select the characteristic sound of any one of a grand, baby grand, upright, or spinet type of piano. The construction of tuned cavities is known to those skilled in the art and therefore it is not necessary to describe the modifications in cavity structure necessary to provide the above-set forth variations in tone or quality.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the nvention.

We claim:

1. An electronic musical instrument including a key opera-ted action, velocity sensitive transducer means for directly transducing the velocity of a struck key into an electric signal proportional thereto, said piano action including a movable core element associated therewith, said velocity sensitive transducer means including a coil, said core element being operative to vary the inductance of said coil in accordance with the velocity of said key, audio output means for producing an audio output in accordance with said transducer means electric signal, and knock producing means, said knock producing means including a soundboard acoustically coupled to said transducer means for broadcasting a sound energy pulse, said pulse being generated by the mechanical shock energy of said piano action striking said transducer means.

2. An electronic piano comprising a key operated piano action, velocity sensitive transducer means for directly transducing the velocity of a struck key into an electric signal proportional thereto, said piano action including a hammer, said hammer being controlled in its movement by said key and having a core element associated therewith, said velocity sensitive transducer means including a coil, said core element being operative to vary the inductance of said coil in accordance with the velocity of said hammer, audio output means for producing an audio output in accordance with said transducer means electric signal, and knock producing means, said knock producing means including a soundboard acoustically coupled to said transducer means for broadcasting a sound energy pulse, said pulse being generated by the mechanical shock energy of said hammer striking said transducer means.

3. In an electronic musical instrument including a key operated action, velocity sensitive transducer means for directly transducing the velocity of a struck key into an electric signal proportional thereto, said action includinga movable core element associated therewith, said velocity sensitive transducer means including a coil, said core element being operative to vary the inductance of said coil in accordance with the velocity of said key, audio output means for producing an audio output in accordance with said transducer means electric signal, and knock producing means, said knock producing means including a tuned circuit coupled to said transducer means for modifying said electric signal to have the frequency characteristics of a knock sound.

4. An electronic musical instrument comprising a plurality of key operated actions, each action having associated therewith a transducer means for directly transducing the movement of a struck key into an electric signal, each said action including a magnetic core, each said transducer means including a coil, said core being operative to vary the inductance of said coil in accordance with the movement of said key, an audio output means for producing an audio output in accordance with said transducer means signal, said audio output means including a plurality of tone generators, at least one tone generator coupled to each transducer means, each tone generator producing a characteristic tone signal in response to said electric signal, said characteristic tone being representative of musical notes, and at least two knock producing means associated 'with distinct groupings of said transducer means, each said knock producing means including a soundboard acoustically coupled to a grouping of said transducer means for broadcasting a sound energy pulse, said pulse being generated by the mechanical shock energy of one of said actions striking one of said transducer means.

5. An electronic musical instrument comprising a plurality of key operated actions, each action having associated therewith a magnetic transducer means for directly transducing the movement of a struck key into an electric signal, each said action including a magnetic core element, each said sensitive transducer means including a coil, said core element being operative to vary the inductance of said coil in accordance with the movement of said key, an audio output means for producing an audio output in accordance with said transducer means, said audio output means including a plurality of tone generators, at least one tone generator coupled to each transducer means, each tone generator producing a characteristic signal in response to said electric signal, said characteristic signal being representative of musical tones, and at least two knock producing means associated with distinct groupings of said transducer means, said knock producing means including tuned circuits coupled to said transducer means for modifying said electric signal to have the frequency characteristics of a knock sound.

6. An electronic musical instrument comprising a plurality of key operated actions, each action having associated therewith a transducer means for directly transducing the movement of a struck key into an electric signal, each said action including a magnetic core element, each sensitive transducer means including a coil, said core element being operative to vary the inductance of said coil in accordance with the movement of said key, an audio output means for producing an audio output in accordance with said transducer means, said transducer coils being positioned in close spatial relationship, and a metallic wrapping surrounding said coils for limiting the extent of their magnetic fields, whereby the magnetic fields generated by said coils are not inductively coupled to adjacent coils.

7. An electronic musical instrument comprising a plurality of key operated actions, each action cooperating with a transducer means for directly transducing the movement of a struck key into an electric signal, said action including a magnetic core element, each said transducer means including a coil, said magnetic core element being operative to vary the inductance of said coil in accordance with the movement of said key, an audio output means for producing an audio output in accordance with said transducer means signal, said magnetic core elements being positioned in close spatial relationship, a magnetic shield adjacent said core elements, said magnetic shield being operative to redirect the magnetic field of said magnetic core elements to prevent their magnetic force fields from interacting.

8. An electronic musical instrument comprising a key operated action, velocity sensitive transducer means f l directly transducing the velocity of a struck key into an electric signal proportional thereto, said action including a hammer, said hammer being controlled in its movement by said key and having a core element associated therewith, said velocity sensitive transducer means including a coil, a support mounting said coil above said hammer and core element, at least a portion of said support being made of a transparent material, said core element being operative to vary the inductance of said coil in accordance with the velocity of said key, an audio output means for producing an audio output in accordance with said trans ducer means electric signal.

9. An electronic musical instrument comprising a key operated action, a velocity sensitive transducer means for directly transducing the velocity of a struck key into an electric signal proportional thereto, said action including a core element connected therewith, said velocity sen sitive transducer means including a coil, said core element being operative to vary the inductance of said coil in accordance with the velocity of said key, audio output means for producing an audio output in accordance with said transducer means electric signal, said audio output means including means for transducing an electric tone signal into an audio output, said last-mentioned means being coupled to a tuned cavity.

10. An electronic musical instrument comprising actuatable key means, transducer means for transducing the mechanical movement of a struck key into an electric signal, audio output means for producing an audio output in accordance with said transducer means electric signal, knock producing means coupled to said transducer means for producing an audible knock sound, said knock prw ducing means including a sound board acoustically coupled to said instrument, and means for conducting to said 1 1 sound board an acoustic pulse generated by movement of an element of said key means into contact with said instrument.

11. An electronic musical instrument comprising a key operated action, transducer means for directly transducing the mechanical movement of a struck key into an electric signal, an action including a movable element connected therewith, said movable element cooperating with said transducer means to induce said electric signal, audio output means for producing an audio output in accardance with the said transducer means electrical signal, means coupled to said transducer means for producing an audible knock sound, said knock producing means including a sound board coupled to an acoustically conductive rod, said rod being coupled to said transducer means for conducting to said sound board an acoustical pulse generated by mechanical contact between said movable element and said transducer means.

12. An electronic musical instrument comprising actuatable key means, transducer means for transducing the mechanical movement of a struck key into an electric signal, audio output means for producing an audio output in accordance with said transducer means electric signal, said audio output means including means for transducing an electric signal into an audio ouput, and means for feeding audio sound vibrations back to the key means, said feed back means including a tuned cavity, said transducing means being coupled to said tuned cavity for radiating the audio output into said tuned cavity, said tuned cavity being mechanically fixed to a casing for said instrument, and said actuatable key means being mechanically mounted to said casing.

13. An electronic musical instrument comprising a key operated action, transducer means for directly transducing the mechanical movement of a struck key into an electric signal, said action including a movable element connected therewith, said movable element cooperating with said transducer means to induce said electric signal, audio output means for producing an audio output in accordance with said transducer means electric signal, and means coupled to said transducer means for producing a knock sound, said knock producing means including a tuned circuit coupled to said transducer means for modifying said electric signal to the frequency characteristics of a knock sound.

References Cited UNITED STATES PATENTS 2,619,866 12/1952 Bailey 84349 2,780,302 2/1957 George 181-31 2,952,179 9/1960 Andersen 841.24 3,248,470 4/1966 Markowitz et a1. 84-126 XR ARTHUR GAUSS, Primary Examiner.

JOHN ZAZWORSKY, Assistant Examiner.

US. Cl. X.R.

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