Are there any requirements for the music in the gamejam?
If you are wanting to make some quick (and pretty good) looping chiptunes on the fly, one of the best sites I've found for this is:
www.beepbox.co
It's quick and easy to use, it's almost impossible to make a bad song, it is set to automatically loop, you can export to .wav .midi or even .json, it's FREE and of course the music is 100% yours! So you don't have to worry about giving credit. ;)
Anyway, I hope this helps, it really works great for what it's worth.