Unmixer does two things: first, it lets you extract loops from any song; second, it lets you remix these loops in a simple interface.
How do I use it?
Upload a song: drag and drop an audio file (MP3, MP4) into the box with the dotted line
Wait for results: processing a new song can take several minutes.
Remix the loops: turn each sound on and off by clicking the box.
Upload more songs: you can mash-up sounds from as many songs as you like.
The BPM indicator in the top right lets you choose the global tempo.
The download button allows you to save a zipfile of all the loops, along with a map of where they occur in the piece.