Online Looping Music Editor

Dubstep Studio (Learning Jam001) - use the CLICK TO MIX button to hear the composition.

I stumbled across a FREE online editor to create loops-based music. The site provides a large number of Midi-loop phrases, and you "paint" the loops along a timeline to indicate when each sound loop should play. After the creation is made, you can embed the music or provide an email link to friends to "remix" your creation.