C.F. Becker, in his _Hausmusik in Deutschland_, has suggested that
these sonatas were known also to Mozart, and begs us to look on this
picture, the opening of a Vivace movement in Kuhnau's 6th Sonata:--

[Music illustration]

and on this, from _The Magic Flute_:--

[Music illustration]

Faisst, however, justly observes that though the harmonic basis is the
same in both, with Kuhnau the under-part is melody, whereas with
Mozart it is the reverse. He also accuses Becker--and justly, as
readers may see by turning to the passage in the _Zauberflöte_--of not
having represented the passage quite honestly. Reminiscence hunters
need to be very careful.

In these sonatas, as compared with the one in B flat, the thematic
material is of greater importance; and so, too, in the slow movements
the writing is simpler and more melodious.

The rapid rate at which they were composed deserves mention. Kuhnau
seems to have had the ready pen of a Schubert. In the preface to these
"Frische Früchte" he says: "I wrote these seven sonatas straight off,
though attending at the same time to my duties (he was _juris
practicus_, also organist of St. Thomas'), so that each day one was
completed. Thus, this work, which I commenced on the Monday of one
week, was brought to an end by the Monday of the following week."