opera star vs vocalizer

opera star and vocalizer both are nouns.

Word	Noun	Adjective	Verb	Adverb
opera star	Yes	No	No	No
vocalizer	Yes	No	No	No

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

Other hypernyms of opera star include singer, vocaliser, vocalist.

opera star (noun)	vocalizer (noun)
singer of lead role in an opera	a person who sings
	an organism that can utter vocal sounds