Heres a triton or synth sampling tip.
Go to your basic parameters and turn off any decay and attack, relase, etc. Setting them all to zero. And turn off all effects.
Then sample it. Then when you have the sample in your mpc4000, you can loop the back end of it, so its got infinite sustain and loops forever. If you turned off all envelop settings, and effects, you can use "find loop" function on the mpc4000, and all the work is done for you

.Then later, re-apply your envelope settings in program mode. ANd add your effects.
You can also go to a "blank patch" then go to your oscilator.....assign just 1 rom sample.........sample that, sample all your rom samples, loop them, then you have the entire rom in your mpc4000. Only thing you have to do then, is recreate some patches!
If its a synthy patch, all you gotta do is Sample C3.....middle "C" on the triton. Then just spread out the sample. If its acoustic you might have to multisample.