System For Producing Musical Tones

Abstract

Prerecorded notes of a musical instrument are stimulated to play by means of a voice-responsive system or instrumental equipment. Magnetic as well as electro-optical storage and retrieval systems are provided in conjunction with control circuit operated by a microphone or other input to convert a voice or keyboard signal, for example, into an output, as from a speaker, wherein the output is in the form of instrumental music.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to systems for producing musical tones and more particularly is directed towards a system for producing musical tones which accurately simulate the tones of a selected musical instrument in response to a vocal or other input.

2. History of the Prior Art

In my copending application Ser. No. 545,463 filed Apr. 26, 1966 now U.S. Pat. No. 3,484,530 and entitled "Musical Instrument Employing Film Sound Track on Cathode Ray Tube Screen," there is disclosed an electro-optical apparatus to produce artificially the tones of a musical instrument from a voice input. A film soundtrack of a musical instrument is applied to a cathode ray tube and a transducer, responsive to the light passed through and modulated by the track, is employed to drive a loudspeaker. The scanning beam of the tube is controlled by an input, preferably vocal as at a microphone. It is an object of the present invention to provide improvements in systems of the foregoing type. It is a further object of the present invention to provide various methods for storing and retrieving prerecorded musical instrument sounds as well as alternate means of detecting which musical note is to be reproduced.

SUMMARY OF THE INVENTION

This invention features a system for producing musical tones in response to a stimulating vocal or instrumental input. The system includes various memory means for storing and retrieving prerecorded musical instrument sounds, including a rotatable drum on which the sounds are recorded on tracks, the output being achieved through electro-optical means. In another embodiment the sounds are magnetically recorded on tape. The system includes various techniques by which the pitch or frequency of the stimulating note can be detected. These include a resonant reed device, a cathode ray tube employing light-sensitive elements and an analog to digital converter using logic circuitry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system for artificially producing musical tones made in accordance with the invention,

FIG. 2 is a somewhat schematic view, in front elevation, of an electro-optical storage and retrieval apparatus comprising a modification of the invention,

FIG. 3 is a somewhat schematic view of the frequency detector made according to the invention,

FIG. 4 is a schematic diagram showing the FIG. 3 detector embodied in a system,

FIG. 5 is a schematic diagram showing a modification of the frequency-sensing system and employing a cathode ray tube,

FIG. 6 is a schematic diagram showing a modification of the frequency detector and employing analog to digital and logic techniques, and,

FIG. 7 is a circuit diagram of a gating circuit made according to the invention and employable in the above systems.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1 os the drawings there is illustrated a system for storing and reproducing prerecorded musical notes. The system includes a microphone 10 through which audio inputs, such as vocal sounds, are fed sequentially to a preamplifier 12, an amplifier 14 and then into a frequency detector 16. The frequency detector is connected to gating circuits 18 to be described more fully below which gating circuits are operatively connected to and receive inputs from musical note storage means 20. This unit includes a magnetic tape 22 on which musical notes are prerecorded and which may include a number of channels. The tape 22 preferably is endless, passing about reels 24 and 26 to reach past a sensing head 28 located opposite tape section 30 spanning between posts 32 and 34. One of the reels 24 or 26 is drivingly connected to a motor 36 which advances the tape at a speed adjusted to produce an accurate note pitch. Assuming the tape has a plurality of channels there will, of course, be provided a magnetic pickup sensor 28 for each channel. The prerecorded musical notes on he tape will be transmitted from the sensor 28 into the gating circuits, the output of the gating circuits being fed to a preamplifier 38, to an amplifier 40 and thence to a speaker 42 providing an audio output. This audio output will be in the form of instrumental music of whatever type which has been prerecorded on the tape 22. Thus, a performer humming or whistling, for example, into the microphone 10 will cause instrumental music to be delivered from the speaker 42, carrying whatever tune is being sung into the microphone.

Referring now to FIG. 2 of the drawings, there is illustrated a modification of the musical tone storage means and in this embodiment an electro-optical system is provided for storing and retrieving prerecorded music. In FIG. 2 there is shown a cylinder 44 carried by a shaft 46 rotatably supported on trunnions 48 and 50. The shaft 46 is driven by means of a motor 52, for example, drivingly connected by means of a belt and pulley arrangement 54. The outer cylindrical surface of the cylinder 44 is made highly reflective to visible and/or infrarays. Disposed on the reflective surface is a plurality of axially spaced annular optical soundtracks 56.

Each optical soundtrack 56 typically is of the type employed along the margins of sound movies and operates by modulating a light beam directed through the moving track. In FIG. 2 a light source 58, visible or infrared, for example, is employed with a lens 60 to focus a beam of light 62 against one of the soundtracks 56 and against the reflective underlying surface of the cylinder 44. As the drum is rotated at its proper speed for true pitch, the reflected light energy contained in the beam 62 is modulated by the moving track and passed through a light-gathering lens system 64 to focus the modulated beam onto a light sensor 66. The arrangement generates one musical note for each sound track and, in practice, each annular track 56 will be provided with an associated light source and detection components. The confiquration is relatively inexpensive and does not require close tolerances. The electro-optical unit is connected to the system between the gating circuits 18 and the amplifying stages 38 and 40 of FIG. 1 and may be substituted for illustrated magnetic unit 20.

Referring now to FIG. 3 of the drawings there are shown details of a frequency detector such as indicated in box form at 16 of FIG. 1. The detector serves to detect the pitch or frequency of the stimulating note.

The frequency detector of FIG. 3 embodies vibrating resonant reed principles. The unit utilizes a transducer 68 which may be a permanent magnet or an electrodynamic loudspeaker for generating sound waves. The transducer is provided with a speaker cone 70 which is drivingly connected by means of a bar or shaft to a rigid plate 74. The plate 74 has mounted thereto one or more overhanging reeds 76 extending into proximity to a stationary conductive member 78. In operation, the speaker cone 70 will vibrate in response to the notes generated at the microphone 10 of FIG. 1 and in the amplification system to which it is connected. This vibration of the cone will cause the plate 74 to vibrate at the same time. As the loudspeaker and plate vibrate, the motion is transmitted to the overhanging reed 76 and, if the reed 76 has an appropriate physical length for the transmitted vibration frequency, it will oscillate in resonance. If the reeds are fashioned from drawn glass with diameters of 1 mm. or less, their natural resonant frequencies will fall into the range of 100 to 1,000 cycles per second and their lengths will measure less than 2 inches. Because the resonant frequencies associated with each reed are so sharp, plus or minus only a few cycles per second, they provide excellent means of detecting audio notes.

The reed 76 is made electrically conductive by coating its entire surface with a good electrically conductive metal such as gold or silver. Alternatively, the reeds may be made of a fine diameter electrically conductive wire. The stationary member 78 is provided so that physical and electrical contact may be made with the vibrating reed to form a switch that is responsive to one discrete electrical signal of that pitch. The switch, comprised of the reed 76 and member 78, is connected to the gating circuit, shown as box 18 in FIG. 1, and serves to stimulate a musical note in the voice-operated system such as shown schematically in FIG. 4. It will be understood that while a single reed is shown in the FIG. 3 detector, additional reeds may be provided for other notes and typically will be mounted adjacent to one another on the plate.

The FIG. 4 system includes a microphone 10' a preamplifier 12', and amplifier 14', a frequency detector 16' and gating circuits 18'. The gating circuits provide control signals to light sources such as the lamp 58 of FIG. 2 the beam of which is modulated by the soundtracks 56 to operate the light sensor 66. The light sensor output is fed to a preamplifier 38', thence through an amplifier 40' to a speaker 42'. Connected between the amplifier 14' and the amplifier 40' is an input output volume slave control unit 80 which serves to maintain the volume level for the system. Connected between the amplifier 14' and the gating circuits 18' is a signal termination detector 82 which provides a control signal to the gating circuitry and will be described more fully below.

Referring now to FIG. 5 there is illustrated a modification of the frequency sensing and switching arrangement and in this embodiment a cathode ray tube 84 is employed to serve the same function as the resonant reed device of FIG. 3. In the FIG. 5 system a microphone 10" is connected through a preamplifier 12" and an amplifier 14" to a frequency voltage converter 86 which controls a horizontal deflection circuit 88 operating the deflection plates of the cathode ray tube 84.

The horizontal deflection voltage for the cathode ray tube is derived from the frequency voltage converter which in turn has been stimulated by the vocal input note. The position of a spot or beam 90 on the face of the cathode ray tube is determined by the frequency input signal and will move in response to changes in the frequency. Disposed across the face of the tube is a plurality of light-sensing elements 92 and 94, etc., and located at positions corresponding to notes on the musical scale. These light-sensitive elements will detect the presence of the beam 90 at these positions by reacting to the light emitted locally by the phosphor coating. The pulses obtained from the activated light sensors are then employed to trigger gating circuits 18" which are used in the arrangement shown to provide musical note playback. In FIG. 5 the gating circuits are employed in connection with the magnetic tape storage and playback system 20 of FIG. 1 or with the electro-optical unit of FIG. 2, either of which provides an output at the loudspeaker. In place of the light sensors 92, 94 and gating elements of the gating circuits 18, photoactivated silicon-controlled rectifiers may be disposed on the face of the tube 84 for direct gating action.

Referring now to FIG. 6 of the drawings, there is shown a further modification of the invention, and in this embodiment the activation frequency is detected by analog to digital conversion and logic circuitry. The conversion system utilizes a ramp technique and the conversion that is made is one from voltage to time, the time being that period required for a ramp voltage of known slope to pass between a reference level and an unknown level. The measured time period will thus be proportional to the voltage of the signal being measured. The particular time period is measured by counting clock pulses of a known frequency as the ramp travels between reference levels. There are other analog to digital and integrating to digital methods which may also be employed to advantage.

In the FIG. 6 system an audio input to the microphone is amplified and delivered to a frequency to voltage converter 96. The analog voltage output of the converter 96 is then fed into an input comparator 98 also having an input from a ramp generator 100 which, in addition, provides an input to a ground comparator 102. Both comparators, in turn, provide inputs through a gate control 104 to a counter 107 which also receives pulses from an electronic clock 108. The clock and counters feed into logic circuitry 109 providing output to gating circuits 18"'. The gating circuits in turn control the operation of light sources 58 for the electro-optical system of FIG. 2 or the sensor in the magnetic tape system of FIG. 1. The FIG. 6 system thus serves as a modification of the frequency detector.

Referring now to FIG. 7 of the drawings, there are shown details of the gating circuit 18 shown in box form in FIG. 1 and other diagrams and which may be employed in all of the systems illustrated. The gating circuit is organized about a plurality of gated silicon-control rectifiers 110, 112 and 114. Typically, the SCR 110 is normally in the off state and the application to its cathode gate 116 of a positive current pulse such as that supplied by the frequency detector at point X.sub.1 in FIG. 3 will cause the SCR 110 to turn on and conduct. Connected in series with each SCR is a lamp 58, 58', 58" etc., each lamp being selectively energized by the associated conducting SCR. In operation, when a different note is sounded into the system without pause, a corresponding gating circuit will be triggered.

In operation, if, for example, the SCR 112 were turned on, the voltage at the point 124 would suddenly fall. Associated commutating capacitors 126, 128, 130, etc., in the respective anode circuits would cause a high negative current pulse to reach SCR 110 reducing its current below the holding point and thus turning off SCR 110. The lamp 58' is now illuminated and the lamp 58 is extinguished. The arrangement provides instantaneous extinguishment of any lamp in the on state by the illumination of any other lamp. The signal termination detector circuit 82, shown in box form in FIG. 4, serves to provide a pulse to the gating circuit. The purpose of this pulse is to extinguish whichever lamp is lit at the end of the input signal, at the microphone, where there is a time lapse between notes. The pulse is fed to the SCR anodes with a coupling capacitor at the point indicated at X.sub.3 of FIG. 7. Extinguishment of any lamp in the on state is accomplished in the same manner. As each light goes on a corresponding instrumental note will be emitted by the loudspeaker. In place of the lamps in the FIG. 2 system, light-emitting diodes may be employed in conjunction with light sensors.

While the invention has been described with particular reference to the illustrated embodiments numerous modifications thereto will appear to those skilled in the art without departing from the scope of the invention. For example, any of the music memory systems can be actuated by means other than a microphone amplifier and frequency detector stages. Switches directly actuated by a keyboard on a piano, for example, may be used to operate selectively the different magnetic pickup heads or light sources as a means of producing musical tones.

Claims

Having thus described the invention what I claim and desire to obtain by Letters Patent of the United States is:

1. A system for converting music of one form into music of another form, comprising

a. electronic receiving means for receiving said one form of music and converting it to electrical signals of changing frequencies,

b. a frequency detector connected to said receiving means for detecting discrete frequencies of said signals,

c. memory means having a plurality of prerecorded notes in another musical form stored therein,

d. selectively operable note retrieval means operatively associated with said memory means,

e. electronic gating means connected to said detector and said retrieval means and responsive to different detected signals from said detector corresponding to different detected frequencies whereby an input signal representing a particular frequency in said one musical form will selectively actuate said retrieval means to stimulate from said memory means a corresponding frequency in the other musical form, and,

f. audio output means connected to said memory means.

2. A system according to claim 1 wherein said memory means includes a multiple channel magnetic tape, driving means for moving said tape and a plurality of sensing heads responsive thereto, said heads being connected to said gating means whereby the output of said heads may be fed selectively to said output means.

3. A system for converting music of one form into music of another form, comprising

a. electronic receiving means for receiving one form of music and converting it to electrical signals of changing frequencies,

b. a frequency detector connected to said receiver means for detecting discrete frequencies of said signals,

c. memory means having a plurality of prerecorded notes in another musical form stored therein,

d. electronic gating means connected to said detector and said memory means and responsive to different signals from said detector corresponding to different detected frequencies whereby an input signal representing a particular frequency in said one musical form will stimulate from said memory means a corresponding frequency in the other musical form, and,

e. output means connected to said memory means,

f. said detector including a support, a plurality of conductive resonant reeds extending from said support, a plurality of contacts connected to said gating means disposed in close proximity to said reeds, and means for oscillating said support in response to the input frequency whereby said reeds will open and close circuits with said contacts according to their resonant frequencies.

4. A system for converting music of one form into music of another form, comprising

a. electronic receiving means for receiving said one form of music and converting it to electrical signals of changing frequencies,

b. a frequency detector connected to said receiving means for detecting discrete frequencies of said signals,

c. memory means having a plurality of prerecorded notes in another musical form stored therein,

d. electronic gating means connected to said detector and said memory means and responsive to different signals from said detector corresponding to different detected frequencies whereby an input signal representing a particular frequency in said one musical form will stimulate from said memory means a corresponding frequency in the other musical form, and,

e. output means connected to said memory means,

f. said detector including a frequency to voltage converter connected to said receiving means, a cathode ray tube having a beam responsive to the voltage from said converter, a plurality of light-sensing elements disposed in register with said tube and connected to said gating means whereby said beam will energize said elements in accordance with changes in said voltage.

5. A system for converting music of one form into music of another form, comprising

a. electronic receiving means for receiving said one form of music and converting it to electrical signals of changing frequencies,

b. a frequency detector connected to said receiving means for detecting discrete frequencies of said signals,

c. memory means having a plurality of prerecorded notes in another musical form stored therein,

d. electronic gating means connected to said detector and said memory means and responsive to different signals from said detector corresponding to different detected frequencies whereby an input signal representing a particular frequency in said one musical form will stimulate from said memory means a corresponding frequency in the other musical form, and,

e. output means connected to said memory means,

f. said detector including a frequency to voltage converter connected to said receiving means, a ramp generator, a pair of voltage comparators one of which is connected to said ramp generator and ground, an oscillator, a gate control connected to said oscillator and said comparators, a counter connected to said gate control, logic circuits, a clock connected to said counter and said logic circuits, said logic circuits being connected to said gating means.

6. A system for converting music of one form into music of another form, comprising

a. electronic receiving means for receiving said one form of music and converting it to electrical signals of changing frequencies,

b. a frequency detector connected to said receiving means for detecting discrete frequencies of said signals,

c. memory means having a plurality of prerecorded notes in another musical form stored therein,

d. electronic gating means connected to said detector and said memory means and responsive to different signals from said detector corresponding to different detected frequencies whereby an input signal representing a particular frequency in said one musical form will stimulate from said memory means a corresponding frequency in the other musical form, and,

e. output means connected to said memory means,

f. said gating means including a plurality of silicon-controlled rectifiers connected in parallel sequence between said frequency detector and said memory means, said rectifiers normally being in a nonconducting mode and adapted to conduct in response to said detector whereby said memory means will be selectively stimulated.