sestet vs sextet

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. 

sextet

noun
  • A composition for six voices or instruments. 

  • Any group of six people or things. 

  • A group of six singers or instrumentalists. 

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