Perfect Harmony is an a cappella musical comedy by Andrew Grosso and The Essentials for Perfect Harmony. A cappella vocal arrangements for Perfect Harmony are by Adam Wachter, with additional arrangements by Ray Bailey and Jeremy Gussin. Bailey and Wachter provided arrangements for the Off-Broadway production. The work premiered at the 2006 New York International Fringe Festival where it had an extended run in the Fringe Encore Series before it opened Off-Off Broadway in 2008. Its Off-Broadway introduction came in an October 2010 opening. The licensing agent for the play is the Samuel French Company

Music performed a cappella, less commonly spelled a capella in English, is music performed by a singer or a singing group without instrumental accompaniment. The term a cappella was originally intended to differentiate between Renaissance polyphony and Baroque concertato musical styles. In the 19th century, a renewed interest in Renaissance polyphony, coupled with an ignorance of the fact that vocal parts were often doubled by instrumentalists, led to the term coming to mean unaccompanied vocal music. The term is also used, rarely, as a synonym for alla breve.