harmonica vs piano accordion

harmonica

noun
  • A musical instrument, consisting of a series of hemispherical glasses which, by touching the edges with the dampened finger, give forth the tones. 

  • A toy instrument of strips of glass or metal hung on two tapes, and struck with hammers. 

  • A musical wind instrument with a series of holes for the player to blow into, each hole producing a different note 

piano accordion

noun
  • an accordion with a keyboard similar to that of a piano 

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