A bootleg recording is an audio or video recording of a performance not officially released by the artist or under other legal authority. Making and distributing such recordings is known as bootlegging. Recordings may be copied and traded among fans without financial exchange, but some bootleggers have sold recordings for profit, sometimes by adding professional-quality sound engineering and packaging to the raw material. Bootlegs usually consist of unreleased studio recordings, live performances or interviews without the quality control of official releases.