The FADER button on the TD-30 lets you choose what can be controlled by the Group Faders.
Each time you press the FADER button, the LED indicator toggles between the upper section and lower section. (KICK / AUX 1).
When the Fader indicator is lit next to "KICK," you'll be able to control the volume levels for the KICK, SNARE, TOMS, HI-HAT, CRASH, RIDE, AUX, and AMBIENCE when moving the faders.
When the Fader indicator is lit next to AUX 1, you'll be able to control the volume levels for AUX 1, AUX 2, AUX 3, AUX 4, CLICK, PATTERN, and the USB SONG.
Note: Fader levels are stored while in each mode.
For example, if you turn down the volume level using the CRASH fader, and then switch to the lower Fader mode (indicator lit next to AUX1) and move the CRASH fader, it will now [only] be controlling the CLICK volume. Since the CRASH level was previously reduced, and the TD-30 stores this information, you'll need to press the FADER button to return to the upper fader section if you want to control the volume level of the CRASH again.