Pioneer Dj DDJ-FLX4 Portable 2-Channel rekordbox DJ and Serato Controller (Graphite) - Manual (Page 128)

rekordbox for iOS/Android
128
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 Using Beat Loop
If you press a Performance Pad, a loop with the number of beats
assigned to the pad is set. The loop keeps playing after you remove
your finger from the pad.
1 Press the [BEAT JUMP] mode button while holding the [SHIFT]
button.
The unit enters Beat Loop mode.
The number of beats set to the Performance Pads are as follows:
The number displayed on each pad shows the number of beats for Beat Jump.
2 Press a Performance Pad.
The loop plays with the number of beats set on that pad.
3 Press the same Performance Pad again.
The loop is canceled and the rest of the track continues to play.