Rapper Troy Ave Drops Track Behind Bars ... I'm Innocent!!!

Rapper Troy Ave proclaims innocence ... sort of ... in a freestyle rap he just dropped from jail.

The rapper -- who's facing attempted murder charges for his role in the shooting at a T.I. concert -- claims he took the gun and turned the tables on the person who tried to assassinate him.

Check out the track ... chilling stuff and probably ill-advised, legally speaking.