A further innovation by Bach was the trio sonatas involving a concertante (obbligato) right-hand harpsichord part in addition to the bass line, plus one melodic instrument, thus for two players. Examples are the six sonatas for harpsichord and solo violin (BWV 1014–1019), three sonatas for harpsichord and viola da gamba (BWV 1027–1029), and three sonatas for harpsichord and flute (BWV 1030–1032).