sing vs descant on

sing and descant on both are verbs.

Word	Noun	Adjective	Verb	Adverb
sing	No	No	Yes	No
descant on	No	No	Yes	No

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

sing (verb)	descant on (verb)
make a whining, ringing, or whistling sound	sing a descant on a main tune or melody
divulge confidential information or secrets
to make melodious sounds
produce tones with the voice
deliver by singing