A cappella is a type of vocal music that is unaccompanied by instruments. It is typically performed by a group of singers, and the term 'a cappella' is derived from the Italian phrase meaning 'in the manner of the chapel.' The most common forms of a cappella are motet, CHOIR, OCTET, and ALTO. A motet is a polyphonic choral composition, usually with Latin lyrics, that is sung without accompaniment. A CHOIR is a large group of singers who perform together, often in a church or other religious setting. An OCTET is a group of eight singers or instrumentalists. Finally, an ALTO is a singer whose vocal range lies between tenor and soprano.