gm_modulation
modulation = vp->chan->gm_modulation + vp->chan->midi_pressure;
modulation = vp->chan->gm_modulation + vp->chan->midi_pressure;
modulation = vp->chan->gm_modulation + vp->chan->midi_pressure;
modulation = vp->chan->gm_modulation + vp->chan->midi_pressure;