If you sing a cover song and change something about the track (whether it be lyrics, timing, key), your cover has now become a derivative work. Think of it as deriving from another piece of music and, therefore, become something new. You will ALWAYS need permission to do these.
Music And Depression
What is music? All sounds are comprised of sound waves. What distinguishes music from other sound waves is the manner in which the sound waves vibrate and decrease from loud to soft.
