Deryk Barker wrote:

>Oddly, and despite the obvious resemblance between the opening theme of
>K491 and Beethoven's Op.37, he seems to have been more inspired by K466,
>for which he composed cadenzas.  And wasn't it K466 of which he said to
>Ries something along the lines of "you and I will never be able to do
>anything like that"?

Actually, it was in fact K491, from which he also borrowed the idea of
the piano playing arpeggios over the orchestra at the end of the first
movement.

Peter Goldstein