Donald Satz wrote:

>Beethoven took a next-to-nothing theme of Diabelli's and created a
>masterpiece.  Does this necessarily mean that Beethoven thought highly
>of the Diabelli theme?  There can be a large number of reasons why one
>composer borrows from another.  I do wonder if we have any documented
>quotes from Bach relating to his opinion of Vivaldi.

I don't know (I'm sure someone else does).  But Bach transcribed complete
Vivaldi concertos (and not just one) which is incomparable to using a
theme as a departure point like Beethoven did with Diabelli.

Philip