I've played around with Stochas, a MIDI sequencer that lets you set each cell to have a certain probability of sounding when the playhead hits it. Kinda fun for certain weirdo stuff that I get into at times. You can also randomize velocity, I believe. I found out last night that Cakewalk's Step Sequencer already has variable note probability built in, when I did a search on the word "randomize." To access this feature, you click the arrow to the left of the note header, then from the m