vocalizer vs songster

vocalizer and songster both are nouns.

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

As nouns, songster is a hyponym of vocalizer; that is, songster is a word with a more specific, narrower meaning than vocalizer:

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