Free Music License?

[Roland Häder]

Hello GNU folks,

this idea came to me when I was listening to the background music of a 
small game called "Trackball":

What abount a license which gurantees that also the music made for a 
software project - GNU GPL'ed or compatible, of course -is *free*?

I mean, we already a license for software (GNU GPL) and also for 
documentation (FDL) but no license for music (FML = Free Music 
License?). But you cannot compare music with software nor 
documentation. Music is different to them.

Just an idea...

Regards,
  Roland Haeder