Collocations for mutter - verb

gruffly, harshly, hoarsely
through clenched teeth, through gritted teeth
‘I don't need a drink,’ she muttered through clenched teeth.

aloud
loudly
quietly, softly, under your breath
silently
sleepily
incoherently, vaguely, weakly
angrily, bitterly, crossly, darkly, fiercely, furiously, grimly, irritably, sourly, sullenly
Helen began muttering darkly about hospitals.

miserably, sadly
nervously
sheepishly
drily, sarcastically

be heard to, hear sb
A number of visitors were heard to mutter that it would not have happened at home.
She heard him mutter an oath under his breath.

about
She muttered something about the incompetence of the office staff.

to
He was muttering incoherently to himself.

Mutter is used with these nouns as the object:
apology, curse, obscenity, prayer, reply, swear word, word