Choir is a musical ensemble.
A musical ensemble, also known as a music group or musical group, is a group of people who perform instrumental and/or vocal music, with the ensemble typically known by a distinct name
 In typical 18th century to 21st century oratorios and masses, 'chorus' or 'choir' implies that there is more than one singer per part, in contrast to the quartet of soloists also featured in these works

