To improve work efficiency of SN ratio measurement of the musical sound generator.

When a command (positions of SW1-SW4) is 1110 at the time a power source is switched on, the musical sound generator is set to a test mode, and starts a wave generating calculation by setting a tone color to a sine wave of 440 Hz, loudness to 100% in DAC(digital-analog converter) output standard, right and left banning coefficients to 100%, respectively, and FAF (frequency accumulate flag) and EGF(envelope generate flag) to 1. Thus, a sine wave waveform is generated by one sound generation channel, and the sine wave sound is outputted from a speaker 15 at a full swing level of DAC. The pass or fail of the SN ratio is judged by evaluation by measuring this sine wave sound or listening by ear. Since a device for generating a sign wave signal to measure the SN ratio is not necessary, nor the connection therefor, the work efficiency of the SN ratio measurement is improved.