From The Collaborative International Dictionary of English v.0.48 [gcide]:
Vocalist \Vo"cal*ist\, n. [Cf. F. vocaliste.]
A singer, or vocal musician, as opposed to an
instrumentalist.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
vocalist
n 1: a person who sings [syn: singer, vocalist, vocalizer,
vocaliser]