chorus vs libretto

chorus

noun
  • A piece of music, especially one in a larger work such as an opera, written to be sung by a choir in parts (for example, by sopranos, altos, tenors, and basses). 

  • The main part of a pop song played after the introduction. 

  • A group of singers and dancers in a theatrical performance or religious festival who commented on the main performance in speech or song. 

  • A song performed by the singers of such a group. 

  • An actor who reads the prologue and epilogue of a play, and sometimes also acts as a commentator or narrator; also, a portion of a play read by this actor. 

  • The improvised solo section in a small group performance. 

  • A simple, often repetitive, song intended to be sung in a group during informal worship. 

  • A group of people, animals, or inanimate objects who make sounds together. 

  • A group of people in a performance who recite together. 

  • An instance of singing by a group of people. 

  • The opinion expressed by such a group. 

  • A group of people who express a unanimous opinion. 

  • The noise or sound made by such a group. 

  • A group of organ pipes or organ stops intended to be played simultaneously; a compound stop; also, the sound made by such pipes or stops. 

  • A group of singers performing together; a choir; specifically, such a group singing together in a musical, an opera, etc., as distinct from the soloists; an ensemble. 

  • A feature or setting in electronic music that makes one instrument sound like many. 

  • A part of a song which is repeated between verses; a refrain. 

verb
  • To sing the chorus or refrain of a song. 

  • To sing (a song), express (a sentiment), or recite or say (words) in chorus. 

  • To express concurrence with (something said by another person); to echo. 

  • To provide (a song) with a chorus or refrain. 

  • To sing, express, or say in, or as if in, unison. 

  • Of animals: to make cries or sounds together. 

  • To echo in unison another person's words. 

libretto

noun
  • The text of a dramatic musical work, such as an opera. 

  • A book containing such a text. 

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