MIDI_CTL_MSB_MAIN_VOLUME
case MIDI_CTL_MSB_MAIN_VOLUME:
case MIDI_CTL_MSB_MAIN_VOLUME:
main_vol = chan->control[MIDI_CTL_MSB_MAIN_VOLUME];
main_vol = chan->control[MIDI_CTL_MSB_MAIN_VOLUME] * vp->reg.amplitude / 127;