quartet vs sestet

quartet

noun
  • A musical composition in four parts, each performed by a single voice or instrument. 

  • A group of four musicians who perform classical music together. 

  • A group of four singers, usually males, who sings together in four-part harmony. 

  • A group of four people or things, particularly 

sestet

noun
  • A piece of music composed for six voices or six instruments; a sextet or sestuor. 

  • The last six lines of a sonnet, forming two stanzas of three lines each. 

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