bass guitar vs rumbling

bass guitar

noun
  • A long-necked and solid-bodied stringed instrument (chordophone), tuned to produce bass or low notes, usually with a fretted fingerboard and four thick strings, and requiring the use of an amplifier. 

rumbling

noun
  • A deep low noise. 

  • A muted sound of complaint or discontent. 

adj
  • Deep- and slow-sounding. 

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