I'm just curious, here, but I'd be interested in finding out what kind of mp3's most people use, so a couple of simple questions, if you don't mind:

Do you make your own MP3's, or do you get third party ones?

If you make your own, are they primarily just recordings of sequences you have on equipment you have, or do you add real instruments, use other keyboards you don't take to the gig, and/or vocals to them?

What's YOUR method, mainly?