Time shared tone keying system in electronic musical instrument

摘要

In an electronic musical instrument, a tone source circuit provides tone signals of audio frequencies representing respective notes in a musical scale. A keyboard circuit provides a keying sequence pulses each existing at such a time slot of time sharing at an ultra-audible rate as is assigned to each of keys being depressed. The tone signals and the respectively corresponding keying sequence pulses are AND-gated respectively and then OR-gated commonly to produce a combined tone signal. The keying sequence pulses are obtained by sequentially scanning all the keys in the keyboard in one sequence, or may be equivalently obtained by scanning the same named keys in different octaves simultaneously and AND-gating with octave representing pulses. Or the octave representing pulses may be omitted by separately processing tone signals octave by octave. The system is suitable for digitalization and for production in IC configuration.