opm_set_voice_sub
void opm_set_voice_sub(int, struct opm_operator *);
opm_set_voice_sub(0x40 + channel, &voice->m1);
opm_set_voice_sub(0x48 + channel, &voice->m2);
opm_set_voice_sub(0x50 + channel, &voice->c1);
opm_set_voice_sub(0x58 + channel, &voice->c2);