alto vs falsetto

alto

noun
  • A person or musical instrument that performs the alto part. 

  • A musical part or section higher than tenor and lower than soprano, formerly the part that performed a countermelody above the tenor or main melody. 

  • An alto saxophone 

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. 

verb
  • To sing or utter in falsetto. 

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