Whenever you use an existing recording that someone else made, even if it's just a small sample, you need a master license. For example, if you sample a portion of a David Bowie song, even if it's a simple bass line, you need a master license. If you record yourself singing over a karaoke track or your choir signing over backing tracks, you need a master license. You might want to use an entire popular original recording, such as for a commercial or corporate video. If so, you need a master license. Other common uses of sound recordings include mash-ups, derivative works, interpolations, advertising campaigns, television, film, stage productions, and retail products. All these uses require a master license.