GB1291078A - System for producing musical tones - Google Patents

Abstract

1291078 Photo-electric apparatus R E RUPERT 17 Dec 1969 61497/69 Heading G1A [Also in Divisions G5 and H3] Music in a first form (e.g. vocal) is converted into a second form (e.g. instrumental) by detecting the instantaneous fundamental frequency of the first form music and reproducing from a stored representation, the corresponding note as played by an instrument in the second form. Detecting the fundamental frequency. The vocal or other input music is picked up by a microphone, amplified and applied to a loudspeaker 68, Fig.3, the cone of which is coupled to a plate 74 carrying a plurality of thin metal or metalized glass rods 76 of different lengths, resonant at different frequencies. The rod which is made to vibrate indicates the fundamental frequency of the input by touching a fixed contact 78. In another embodiment, the input signal is applied to a frequency to voltage converter 86, Fig. 5, the output of which is applied to deflect the beam of a cathode ray tube 84. The spot on the tube energizes one of a plurality of photo-detectors 92, 94 which may be light-sensitive silicon controlled rectifiers in gating circuits to indicate the fundamental frequency of the input. In another embodiment, Fig. 6 (not shown) the frequency dependent voltage is compared with a ramp voltage to provide, by gating oscillator pulses, a digital indication of the fundamental frequency. Production of the output tones. Notes produced by the instrument it is desired to simulate may be recorded on multi-track magnetic tape loops, Fig. 1 (not shown) and the appropriate track read by gating circuits in response to the fundamental frequency detected. In another embodiment Fig. 2 (not shown), the notes are recorded as variable reflective bands around the circumference of a motor driven drum. Each band is provided with a lamp or light emitting diode and a photodetector to receive light or infrared reflected from the bands. The appropriate band is selected by energizing the corresponding light source. In another embodiment, the notes are recorded as parallel vertical tracks on the face 202, Fig. 8, of a cathode-ray-tube 201. The frequency dependent voltage produced by converter 215 is used to deflect the beam 203 to the appropriate track and a saw-tooth generator 210 makes the beam scan selected track. Light modulated by the track is reflected by a concave mirror 206 (or condensed by a lens) on to a silicon detector or photo-multiplier 208, the output of which is connected to a loudspeaker 219. Vibrato in, and the amplitude of, the input are detected at 217 and 221 respectively and transferred to the output by modulation of the tube cathode potential. In a modification, Fig. 9 (not shown) only one track is provided for each instrument to be simulated and the frequency of the note produced is varied by varying the frequency of the vertical deflection generator.