In music, a song is a composition that contains vocal parts ("lyrics") that are performed ("sung"), commonly accompanied by musical instruments, exception in the case of a cappella songs. The lyrics of songs are typically of a poetic, rhyming nature, although they may be religious verses or free prose.
Songs are typically for a solo singer, though they may also be in the form of a duet, trio, or larger ensemble involving more voices. See part song. (Works with more than one voice to a part, however, are considered choral.) Songs can be broadly divided into many different forms, depending on the criteria used. One division is between "art songs", "pop songs", and "folk songs". Other common methods of classification are by purpose (sacred vs secular), by style (dance, ballad, Lied, etc.), or by time of origin (Renaissance, Contemporary, etc.).

Three singers, a trio, singing a song while accompanied on a lute played by one of the singers. Das Konzert [The Concert] (c. 1490, Lorenzo Costa).