 "The Art of Fugue" by Johann Sebastian Bach, for example, can be played on a keyboard instrument (harpsichord or organ) or by a string quartet or a string orchestra.The instrumentation of trio sonatas was also often flexibly specified; some of Handel's sonatas are scored for "German flute, Hoboy [oboe] or Violin" Bass lines could be played by violone, cello, theorbo, or bassoon, and sometimes three or four instruments would join in the bass line in unison.Sometimes composers mixed movements for chamber ensembles with orchestral movements.