i chop up the sample on edison and i drag and drop the chop on the step sequencer

then, i set the samples to cut thems (right-click on channel for option to pop up)

i then open up the channel settings window and right-click on the sample waveform at the botoom

a 'detect tempo' option shows up, click it...then select a tempo range i am comfortable with (usually 75-150bpm)
-this is for time stretching

there is a knob for pitch above the 'pre-computed effects' within the channel settings window...u can use this to change pitch without screwing ur tempo

when triggering ur samples, place them on sequencer...to stop a sample, reduce a note's velocity to zero