Patent GB-1395376-A (GB)
Title: Waveform producing means
IPC: G10H7/04
Filed: 1972-07-31
Abstract: 1395376 Electrophonic musical instruments NIPPON GAKKI SEIZO KK 31 July 1972 [31 July 1971 (2) 16 Sept 1971 22 Sept 1971] 35619/72 Heading G5J An electronic musical instrument has a waveform shaper comprising analogue samples of a waveform stored on voltage divider networks and means to read-out the samples by means of pulses so controlled by frequency dividers that the number of samples of the waveform read-out is reduced with increases in the tone frequency to limit the range of sampling frequency. Overall organization of the instrument.- Waveform memories 5a-5d, Fig. 16, containing analogue samples of different voice waveforms are selectable by switches SW1-SW4 operated by tabs TA1-TA4. Each key of the keyboard 1 has a corresponding key switch 2 controlling an oscillator 3 producing a frequency (n.f)/m where n is the number of samples in each memory 5a-5d, f is the frequency of the note and m is the octave in which the note is located. The pulses from oscillator 3 are fed to a point on a frequency divider corresponding to the octave. The divider controls a decoder which sequentially interrogates the stored samples and applies the samples to an amplifier 12 and loud-speaker 13 by way of an expression pedal EP. The amplitude of the samples so applied is controlled by a voltage on line L 1  responsive to attack, decay and sustain controls and a touch responsive circuit. Waveform read-out.-Memory 5 and counter 4 may be combined in a MOS integrated circuit, Fig. 5. The samples are stored in the form P-type diffused resistors P 1 -P s  terminated by an aluminium layer MD(Al) deposited in the waveform desired. The resistors form voltage dividers with a common load resistor (not shown) and the output is taken from the junction point T out . The samples are read sequentially by energizing MOSFETs TR1-TR8 formed by depositing an aluminium gate electrode over the P-type source and drain regions. The MOSFETs TR1-TR8 are controlled by a decoding matrix of MOSFETs MS1-MS4 &c. which receive the outputs of a flip-flop divider chain FF1-FF3 fed by the pulses from oscillator 3. Attack, sustain and decay.-The leading edge of a key actuation signal detected at 11a starts a counter 9, Fig. 2, counting pulses from a clock 9a to sequentially read an attack envelope from a memory 6a, similar to the tone waveform memories to the line L 1 . When the count in 9 terminates, gate 8 switches on a fixed voltage generator 7 to sustain the note until release of the key is detected at 11b. The output of 11b also starts a decay counter which reads out a stored decay envelope to line L 1 . Tabs AT 1  AT 2  vary the attack and decay rates by altering the frequency of clocks 9a, 10a. Touch responsive circuit AND gate 84 being normally enabled by a signal on line c passes pulses to AND gate 85 as soon as the key switch 81s leaves the contact 81a. Pulses continue to pass until the switch 81s reaches contact 81b thereby putting an inhibit on line c. The pulses passed, the number of which depends on the speed of key actuation, are fed to a counter comprising flip-flops 86 and decoder 87 so that the voltage read out of a MOSFET store 89 and fed to the attack/sustain/decay circuit as a scaling factor is selected in dependence on touch.