double bass vs psaltery

double bass

noun
  • The largest stringed instrument of the violin family. 

  • The deepest of all male voices. 

psaltery

noun
  • A zither-like musical instrument consisting of a soundboard with multiple strings, played by plucking the strings with the fingers or a plectrum. 

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