Abstract: When a desired rhythm is selected by a rhythm key group, corresponding rhythm data is set in a rhythm register in a CPU. Meanwhile, accompaniment pattern data is set in bass, backing and arpeggio registers by operation of corresponding bass, backing and arpeggio switches. The data set in the registers are supplied as address data to an arpeggio memory section, a backing memory section and a base memory section, so that corresponding rhythm data, tone color data and accompaniment data are read out.

Abstract: A ROM has 16 memory locations of addresses No. 0 to No. 15. Bass pattern data for the first bar are stored in the memory locations of the addresses No. 0 to No. 7, and bass pattern data for the second bar are stored in the memory locations of the addresses No. 8 to No. 15. The memory locations of the addresses No. 0 to No. 7 are specified by respective counts "0" to "7" of a hexadecimal counter, and the memory locations of the addresses No. 8 to No. 15 are specified by respective counts "8" to "15" of the counter. The output of the counter for the counts "8" to "15" is supplied through a gate circuit to the ROM. The gate circuit is inhibited by the output of a chord designating key section.