In music, a single is a type of release, typically a song recording of fewer tracks than an LP record or an album. This can be released for sale to the public in a variety of formats. In most cases, a single is a song that is released separately from an album, although it usually also appears on an album. Typically, these are the songs from albums that are released separately for promotional uses such as digital download or commercial radio airplay and are expected to be the most popular. In other cases a recording released as a single may not appear on an album.