crooner vs vocalizer

crooner and vocalizer both are nouns.

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

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

Other hypernyms of crooner include singer, vocaliser, vocalist.

crooner (noun)	vocalizer (noun)
a singer of popular ballads	a person who sings
	an organism that can utter vocal sounds