The Sonata in G Major for viola da gamba and continuo (BWV 1027) is probably an arrangement Bach made of his Trio Sonata for two flutes and continuo (BWV 1039). Another version, a trio sonata for organ, also exists. In three movements instead of four, this version is probably not by Bach.
Nonetheless, I love this trio sonata, in all its forms. Enjoy this version with cellist, Anner Bylsma and organist, Bob van Asperen.