In the Sample Edit screen, you have the option to loop your sample by pressing the loop button under the Trim tab.
The loop button will allow you to cycle between the four modes:
Forward: When the loop reaches its end point, it will start playing again from the loop point.
Reverse: When the loop reaches its end point, it will play in reverse. When it reaches the loop point again, it will return to the end point and continue playing in reverse.
Alternating: When the loop reaches its end point, it will play in reverse. When it reaches the loop point again, it will start playing forward again from the loop point. To switch between Forward and off, press and hold Shift, and then tap Loop at the bottom of the screen.
When the loop button is activated, your MPC pads will be assigned to the following functions...
Play Sample (One Shot) (Pad 10) plays the sample once from the start point to the end point. Press the pad once to play it.
Play Sample (Note On) (Pad 11) plays the sample once from the start point to the end point. Press and hold the pad to play it, and release the pad to stop playing it. Alternatively, select the headphones icon in the upper-right corner, and then tap and hold your finger on the waveform.
Play Loop Continuous (Pad 16) plays the sample repeatedly using the mode set by the Loop button (Forward, Reverse, or Alternating; if the Loop button is off, the sample will loop forward repeatedly).
Play Loop (Pad 13) plays the sample repeatedly using the mode set by the Loop button (Forward, Reverse, or Alternating; if the Loop button is off, the sample will loop forward repeatedly). Press and hold the pad to play it, and release the pad to stop playing it.
Play to Loop Start (Pad 14) plays the part of the sample just before the loop point. Press and hold the pad to play it, and release the pad to stop playing it.
Play from Loop Start (Pad 15) plays the sample from the loop point to the end of the sample regardless of the end point. Press and hold the pad to play it, and release the pad to stop playing it.
Play All (Pad 9) plays the entire sample.
Pads 1–4 have the same respective functions as Pads 5–8, but Pads 1–4 play the sample part as “One Shots” (pressing the pad once will play the entire part) while Pads 5–8 play the sample part as “Note Ons” (pressing the pad and holding it will play the part; releasing it will stop playback):
Play from Start (Pad 1, Pad 5) plays the sample from the start point to the end point.
Play to Start (Pad 2, Pad 6) plays the part of the sample just before the start point to the start point.
Play to End (Pad 3, Pad 7) plays the part of the sample just before the end point to the end point.
Play from End (Pad 4, Pad 8) plays the part of the sample from the end point to the end of the sample.