Barenreiter BA8170 - Johann Sebastian Bach Sonata in G minor BWV 1020 for flute and obbligato harpsichord (piano). The flute sonata in G minor BWV 1020, one of the gems of 18th century flute literature, has been passed down to us over the years as a work of Johann Sebastian Bach but its authenticity is disputed. Recent research suggests that the composition most probably came from the pen of Bach’s oldest son Carl Philipp Emanuel.