vocalize vs sing

vocalize and sing both are verbs.

Word	Noun	Adjective	Verb	Adverb
vocalize	No	No	Yes	No
sing	No	No	Yes	No

As verbs, sing is a hypernym of vocalize; that is, sing is a word with a broader meaning than vocalize:

vocalize (verb)	sing (verb)
pronounce as a vowel	make a whining, ringing, or whistling sound
express or state clearly	divulge confidential information or secrets
utter with vibrating vocal chords	to make melodious sounds
utter speech sounds	produce tones with the voice
sing (each note a scale or in a melody) with the same vowel	deliver by singing