Last week Jet Set and Electronic Arts unveiled the limited beta of Music Construction Set: The Blues. It isn't so much a game (yet) as it is an experiment. It let's you rock out with your plastic guitar controller. ...on YouTube.
Here, I'll let Dr. Fantastic, aka Owen, explain it better.
The YouTube channel where you can find more information including the download link, instructions, FAQ and videos of people rocking out is http://www.youtube.com/profile?feature=iv&user=1louderthan10.
Check it out, Rock out, I'm out...
EDIT: Added the Logo, fixed the link.