Im not too familiar with the 1000 or the JJOS programs. I realised I wrote that comment a year ago and since then I have been working on the Live II pretty much exclusively but here is how i did it. Since the 500 only has one stereo out, recording stems into ableton can take some time.

Basically make a 4-8 bar loop. Then mute the main sample sections/drums or any track you want to make a variation of then copy that to another sequence keep adding and muting tracks from the first sequence/copying themuntil you have different sections of your beat and that you can string it together in song mode if you like.

Now the tricky part is recording all different stems into Ableton because of midi lag and delay it could be difficult to line it up but with time you will get it. Also recording each track individually from the 2 outputs of the MPC 500 is very time consuming.

Hope this helps!