sing vs vocalise

sing and vocalise both are verbs.

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

As verbs, vocalise is a hyponym of sing; that is, vocalise is a word with a more specific, narrower meaning than sing:

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