instrument vs plectrum

instrument

noun
  • A device used to produce music. 

  • A legal document, such as a contract, deed, trust, mortgage, power, indenture, or will. 

  • A means or agency for achieving an effect. 

  • A tool, implement used for manipulation or measurement. 

  • A person used as a mere tool for achieving a goal. 

  • A measuring or displaying device. 

verb
  • To devise, conceive, cook up, plan. 

  • To perform upon an instrument; to prepare for an instrument. 

  • To apply measuring devices. 

plectrum

noun
  • A small piece of plastic, metal, ivory, etc., for plucking the strings of a guitar, lyre, mandolin, etc. 

  • A projection of bone or other stiff tissue, such as the ridges in some insects' stridulatory organs. 

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