Music shake is an online music creation tool that lets you create your own original music track from thousands of copyright-free music samples.
To make music, choose a music style from the bottom of the screen, and then click in the squares to add layers of different instruments. Some blocks of music – such as the drum beats, can be altered once added. Clicking the numbers at the top will change the chord for that block.
It’s good fun and I was able to create a short loop of music very quickly.
You need to register with the site to save your clips, but registration is free. The T&C does state that no under 13s should use the site, so keep that in mind when planning to use this with your class.
Check it out at : http://eng.musicshake.com/create
Update : A paid for, educational version of Music Shake is also available. You can take a look at http://edu.musicshake.com/