songster vs vocalist

songster and vocalist both are nouns.

Word	Noun	Adjective	Verb	Adverb
songster	Yes	No	No	No
vocalist	Yes	No	No	No

As nouns, vocalist is a hypernym of songster; that is, vocalist is a word with a broader meaning than songster:

Other hypernyms of songster include singer, vocaliser, vocalizer.

songster (noun)	vocalist (noun)
any bird having a musical call	a person who sings
a person who sings with skill
a composer of words or music for popular songs