A mashup or bootleg[1] (also mesh, mash up, mash-up, blend and bastard pop/rock) is a song or composition created by blending two or more pre-recorded songs, usually by overlaying the vocal track of one song seamlessly over the instrumental track of another.[2] To the extent that such works are 'transformative' of original content, they may find protection from copyright claims under the "fair use" doctrine of copyright law