songster vs vocalizer

songster and vocalizer both are nouns.

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

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

Other hypernyms of songster include singer, vocaliser, vocalist.

songster (noun)	vocalizer (noun)
any bird having a musical call	a person who sings
a person who sings with skill	an organism that can utter vocal sounds
a composer of words or music for popular songs