soften vs mute

soften is not a noun while mute is a noun.

Word	Noun	Adjective	Verb	Adverb
soften	No	No	Yes	No
mute	Yes	Yes	Yes	No

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

Other hyponyms of soften include damp, dampen, dull, muffle, tone down.

soften (noun)	mute (noun)
	a device used to soften the tone of a musical instrument
	a deaf person who is unable to speak

soften (adjective)	mute (adjective)
	expressed without speech
	unable to speak because of hereditary deafness

soften (verb)	mute (verb)
become soft or softer	deaden (a sound or noise), especially by wrapping
make soft or softer
lessen in force or effect
make less severe or harsh
protect from impact
make (images or sounds) soft or softer
give in, as to influence or pressure