><< Here's what I think of a cadenza:
No doubt Bradley will give us the definitive word, but my music master at
school said that the cadenza was a solo section in a concerto usually
sketched in by the composer (basic chord sequences, key changes and the
like) so that the performer had something to go by. You didn't have to
vary what the composer had sketched in but it was usually better to do so
because the sketched music was pretty boring (although I think some
composers wrote pretty good cadenzas and expected performers to stick
rigidly to them).