instrument vs second-stringer

instrument

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

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

  • A device used to produce music. 

  • A means or agency for achieving an effect. 

  • A tool, implement used for manipulation or measurement. 

  • 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. 

second-stringer

noun
  • A person who is not good enough to be considered proficient but may be useful as a backup. 

  • A person who plays second string. A person who is kept on a sports team as a backup in case a "first-string" player is unavailable. 

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