guitar vs hammered dulcimer

guitar

noun
  • A stringed musical instrument, of European origin, usually with a fretted fingerboard and six strings, played with the fingers or a plectrum (guitar pick). 

  • Any type of musical instrument of the lute family, characterized by a flat back, along with a neck whose upper surface is in the same plane as the soundboard, with strings along the neck and parallel to the soundboard. 

verb
  • To play the guitar. 

hammered dulcimer

noun
  • A type of dulcimer whose metal strings are stretched over a trapezoidal sounding board that has two bridges, one bass and one treble, set on a stand and played with small mallet-like hammers. 

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