A mashup (also mesh, mash up, mash-up, blend, bootleg 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. To the extent that such works are "transformative" of original content, in the United States they may find protection from copyright claims under the "fair use" doctrine of copyright law.