The Mute Group feature in the SPD-SX lets you assign a specific pad (or set of pads) so it stops playing when another pad is hit.
For example, if pad #1 and # 5 are assigned to the same Mute Group number, hitting pad #1 will automatically stop pad #5 if it is playing and vice-versa. This can be useful if you have a "phrase" type wave playing on pad #5, and you want it to stop playing automatically as soon as you hit pad #1.
Here's how to access and assign Mute Groups to pads.
1. Select a Kit to edit.
2. Press MENU.
3. Use the cursor buttons to highlight the "PAD" icon, and then press ENTER.
4. Press cursor up or down to select "MUTE GROUP."
5. Hit one of the pads that you'd like to setup a Mute Group for.
6. Press + or - to choose a desired Mute Group number for the pad (1-9).
7. Hit the other desired pad that you want to assign a Mute Group number for.
8. Press + or - to choose the same Mute Group number for the pad from step 6.
9. Repeat the Steps for any remaining pads as desired.
10. When you're finished, press the KIT button. The new settings are saved automatically.