murmuring vs mutter

murmuring and mutter both are nouns.

Word	Noun	Adjective	Verb	Adverb
murmuring	Yes	Yes	No	No
mutter	Yes	No	Yes	No

As nouns, murmuring and mutter are synonyms defined as:

Other synonyms of murmuring include grumble, grumbling, murmur, muttering.

As nouns, murmuring and mutter are synonyms defined as:

murmuring and mutter: a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech

Other synonyms of murmuring include murmur, murmuration, mussitation, muttering.

murmuring (noun)	mutter (noun)
a complaint uttered in a low and indistinct tone	a complaint uttered in a low and indistinct tone
a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech	a low continuous indistinct sound; often accompanied by movement of the lips without the production of articulate speech

murmuring (adjective)	mutter (adjective)
making a low continuous indistinct sound

murmuring (verb)	mutter (verb)
	make complaining remarks or noises under one's breath
	talk indistinctly; usually in a low voice