PURPOSE: To enable effect addition processing of high quality without using a dedicated DSP chip when a system is constituted by using sound source LSIs of plural chips including the sound source LSIs having DSP for effect addition inside.

CONSTITUTION: In the master and slave sound source LSIs 104 and 105, time- vision musical 6ound signals from a musical sound signal generator are divided into four different groups, channel by channel, weighted with mutually different coefficients, and accumulated. Four kind of accumulation outputs obtained by the master sound source LSI 105 are transferred to the slave sound source LSI 104, which adds them to the respective accumulation outputs obtained by itself. The addition results are transferred to the master sound source LSI 105 after the effect addition processing is performed by the DSP of the slave sound source LSI 105, and effect is further added by the DSP of the master sound source LSI. Its output is outputted to a D/A converter 108.