falsetto vs mutter

falsetto

verb
  • To sing or utter in falsetto. 

noun
  • A person who sings in falsetto. 

  • The "false" (singing) voice in any human, usually airy and lacking a purity of vowels; created by utilizing the next highest vocal folds above those used for speech and normal range singing. It is commonly confused with the head voice register. 

mutter

verb
  • To speak softly and incoherently, or with imperfect articulations. 

  • To make a sound with a low, rumbling noise. 

  • To utter words, especially complaints or angry expressions, indistinctly or with a low voice and lips partly closed; to say under one's breath. 

noun
  • A repressed or obscure utterance; an instance of muttering. 

  • Peas. 

How often have the words falsetto and mutter occurred in a corpus of books? (source: Google Ngram Viewer )