off-key vs false

off-key and false both are adjectives.

Word	Noun	Adjective	Verb	Adverb
off-key	No	Yes	No	No
false	No	Yes	No	Yes

As adjectives, off-key and false are synonyms defined as:

Other synonyms of off-key include sour.

off-key (adjective)	false (adjective)
inaccurate in pitch	not in accordance with the fact or reality or actuality
	not genuine or real; being an imitation of the genuine article
	adopted in order to deceive
	designed to deceive
	(used especially of persons) not dependable in devotion or affection; unfaithful
	arising from error
	inaccurate in pitch
	deliberately deceptive
	erroneous and usually accidental
	inappropriate to reality or facts

off-key (adverb)	false (adverb)
	in a disloyal and faithless manner