let on vs sing

let on and sing both are verbs.

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

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

let on: make known to the public information that was previously known only to a few people or that was meant to be kept a secret
sing: divulge confidential information or secrets

let on (verb)	sing (verb)
make known to the public information that was previously known only to a few people or that was meant to be kept a secret	make a whining, ringing, or whistling sound
	divulge confidential information or secrets
	to make melodious sounds
	produce tones with the voice
	deliver by singing