Mats Norrman wrote:

>* Mozart borrowing from M.Haydn: Symphony nr.37, was to great extent
>originally a concert by Haydn.

No.  What was published in the last century as "Symphony #37 by Mozart"
(K. 444) is in reality a symphony by Michael Haydn with a slow introduction
added by Mozart.  There is no borrowing involved, not in the sense
discussed in this thread.  The confusion arose because Mozart not only
wrote the slow introduction, but he also started copying the score of
Haydn's symphony, and from the existence of this manuscript, partially in
Mozart's own hand, it was concluded that the work was written entirely by
Mozart.  At that time - second half of the 19th century - Michael Haydn's
output was practically unknown, and nobody realized that the work was
almost entirely by Haydn.

-Margaret