Could not find this in the manual.

I have some synth samples assigned to pads and would like the sound to continue or just loop as long as I have the pad held down. How do I accomplish this?

In program mode, set the sample to NOTE ON by clicking the WINDOW button. Then pull up your sample in TRIM mode and set the LOOP setting to ON. Adjust your start and end points to get the loop exactly how you want it.

As a sidenote, I have found that the JJ OS allows you to trim your samples much faster than the Akai OS because you no longer have to use the SHIFT plus the cursor button to zoom in or out. It's little things like that I've found all over the JJ OS that makes it a joy to work with.

Good luck!

are they samples that you played and recorded into your mpc? if so, either do what the guy above said or just record the synth notes longer like 10 seconds and that should make it long enough.