SD-80: Muting a Part
Use the following procedure to mute a Part:
1. Press INST so it is lit.
2. Press PART < or PART > to select the part you wish to mute.
3. While holding SHIFT, press PART < to MUTE the part you have selected.
NOTE: Holding SHIFT plus PART < a second time will un-MUTE the part and make it active again.