castrato vs vocalizer

castrato and vocalizer both are nouns.

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

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

castrato: a male singer who was castrated before puberty and retains a soprano or alto voice
vocalizer: a person who sings

Other hypernyms of castrato include singer, vocaliser, vocalist.

castrato (noun)	vocalizer (noun)
a male singer who was castrated before puberty and retains a soprano or alto voice	a person who sings
	an organism that can utter vocal sounds