Tap Mark button to add/remove a marker.
Press-hold Mark to remove all markers.
Tap A to set loop start.
Double-tap A to shift entire loop.
Press-hold A to move loop start to start of song.
Tap B to set loop end.
Double-tap B to shift entire loop.
Press-hold B to move loop end to end of song.
Tap Loop to enable/disable looping.
Press-hold Loop to disable loop and reset A/B to start/end.
Double-tap Loop to set A/B to nearest markers.