A bootleg recording is an audio or video recording of a performance that was not officially released by the artist or under other legal authority. The process of making and distributing such recordings is known as bootlegging. Recordings may be copied and traded among fans of the artist 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 either unreleased studio recordings or live performances, with an unpredictable level of quality.