falsetto vs murmur

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. 

murmur

verb
  • To say (something) indistinctly, to mutter. 

  • To speak or make low, indistinguishable noise; to mumble, mutter. 

noun
  • The sound made by any condition which produces noisy, or turbulent, flow of blood through the heart. 

  • A muttered complaint or protest; the expression of dissatisfaction in a low muttering voice; any expression of complaint or discontent. 

  • Soft indistinct speech. 

  • Any low, indistinct sound, like that of running water. 

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