GB1515181A - Electronic musical instruments - Google Patents

Abstract

1515181 Electronic musical instruments WURLITZER CO 7 May 1975 [3 June 1974] 19081/75 Heading G5S In a tone generator the array 12 of keys 13 is scanned sequentially by decoders 20, 21 so that on detecting a key closed a pulse is generated on line 48 which is used to enable the decoder circuit 68 in order to access ROM 67 and provide control pulses to a plurality of gate circuits 110, a basic frequency (500 KHz) being divided by a plurality of programmable dividers 100 set by the ROM 67 output and the gate circuits 110 and subsequently being transduced to give an audio tone. With the switches 46, 47 as shown the system is in a "lockout" mode (i.e. on closing a key the scan is halted until the tone no longer sounds) and with the switches both reversed the system is in a low note or high note "priority" mode (i.e. the scan continues, but is ignored until the end of the scan). Associated with each programmable divider is a gating circuit 110 which divides by 1 or 2 and a series of flip-flops (see Fig. 4, not shown) which generate octavely related outputs at each stage of the series. The system may be modified so that a plurality of keys may be played simultaneously, e.g. to play four keys there must be at least four dividers, there being a decoding circuit 68 and a ROM 67 for each four dividers. The tone generator may be on a single-integrated circuit. An output on line 65 can be used for controlling percussive voices from the keyboard.