A cover band (or covers band), is a band that plays mostly or exclusively cover songs. New or unknown bands often find the cover band format marketable for smaller gigs, and these bands may be known as a wedding band, party band, and function band. A band whose covers consist mainly of songs that were chart hits is often called a top 40 band. Many bands, however, start as cover bands and then grow to perform original material. For example, the Rolling Stones released three albums consisting primarily of covers before recording one of original material.