"Bach(?)" is the name of the composer on the cover of the Sonata in G minor for flute (violin) and harpsichord, which has two opus numbers: BWV 1020 and H. 542.5. The two numbers refer to Johann Sebastian and Carl Philipp Emanuel, father and son, but even the family connection must be questioned. This, at least, is what editor Barthold Kuijken believes, which also explains the big question mark. According to Kuijken, the work is "much too thin for the father, untypical of Carl Philipp Emanuel, too good for Quantz – and no other composers suggest themselves." In addition to the question of authorship, Kuijken knowledgeably takes on all the other problems raised by the sources, and provides expert comments on stylistic matters. The sonata had not been available from Breitkopf until now; this new edition systematically continues Kuijken’s project of revising the Bach flute sonatas.

"I am very, very impressed by the Breitkopf / Kuijken edition of Bach's flute sonatas that I bought yet another copy when I discovered to my horror that I was en route to a recital abroad without my music. Breitkopf (make sure it's the new edition by Barthold Kuijken you buy) publish each sonata separately,  which inevitably works out more expensive, but with the amount of extra information and inclusion of flute and bass parts together this is a bargain. Everyone should have these, even if they already possess other editions." (Pan Magazine)