The Collaborative International Dictionary of English v.0.48:
Chorister \Chor"is*ter\, n. [See Chorus.] 1. One of a choir; a singer in a chorus. --Dryden. [1913 Webster] 2. One who leads a choir in church music. [U. S.] [1913 Webster]WordNet (r) 3.0 (2006):
chorister n 1: a singer in a choir