intone vs sing

intone and sing both are verbs.

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

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

intone (verb)	sing (verb)
recite with musical intonation; recite as a chant or a psalm	make a whining, ringing, or whistling sound
speak carefully, as with rising and falling pitch or in a particular tone	divulge confidential information or secrets
utter monotonously and repetitively and rhythmically	to make melodious sounds
	produce tones with the voice
	deliver by singing