contrabass vs string bass

contrabass

noun
  • Double bass; string bass. 

  • Any of the several contrabass instruments. 

  • The person or instrument performing the contrabass part. 

  • The part or section one octave lower than bass. 

string bass

noun
  • Synonym of double bass (“lowest-pitched of instruments of violin family”). 

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