A remix is an alternative version of a song, different from the original version. A remixer uses audio mixing to compose an alternate master recording of a song, adding or subtracting elements, or simply changing the equalization, dynamics, pitch, tempo, playing time, or almost any other aspect of the various musical components. Some remixes involve substantial changes to the arrangement of a recorded work, but many are subtle, such as creating a "vocal up" version of an album cut that emphasizes the lead singer's voice. A song may be remixed to give a song that was not popular a second chance at radio and club play, or to alter a song to suit a specific music genre or radio format. Remixes should not be confused with edits, which usually involve shortening a final stereo master for marketing purposes