Make your own remixes at YourSpins.
YourSpins has worked together with musicians to provide you with tracks that you can play with. This means each songs will have multiple instruments for you to choose from. And because all the tracks are provided, you won't run into issues of certain parts not being in tempo or instruments playing in the wrong key.
When you're done, the completed remix will be saved to your YourSpins page where others can listen to your mix. Points are given out depending on how well your mixes are received. Overall points are grouped in levels ranging from "Noob" on up to the "Omnipotent Grand Overlord".