Abstract: On a casing of an electronic keyboard instrument, there are provided front speakers, rear speakers and upper speakers as non-front speakers, a woofer speaker, and a vibrator. Tone generator section generates tone signals of tone colors corresponding to tones of various musical instruments. Assignment section adjusts, on a tone-color-by-tone-color basis, tone volume allocations, of the generated tone signals, to the speakers and vibrator. Further, the thus-adjusted tone signals are mixed for each of speaker reproduction systems and vibrator drive system, and then the resultant mixed tone signals of the speaker reproduction systems and vibrator drive system are supplied to corresponding ones of the speakers and vibrator.