full score vs libretto

full score

noun
  • a large book showing all the notes of a composition with many simultaneous parts (instruments or voices), with all the parts shown in lines underneath each other in a fixed order. Commonly used by conductors. 

libretto

noun
  • A book containing such a text. 

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

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