On Beethoven's "preparation" vs. "spontaneity":

The two aren't mutually exclusive.  Apparently, one of the most remarkable
things about Beethoven the musician was his improvising.  There's all
sorts of contemporary comment on it - how beautiful and how strange, etc.
Many of Beethoven's developments - indeed, the way he puts together themes
from cells - seem to reveal a composer who worked at least in part by
improvising:  ringing one change after another on the cells.  However,
unlike many composers who work this way, Beethoven also had an incredible
sense of architecture.  It's unlikely anyone could improvise the Missa
Solemnis.  The effects are too complex, and, of course, it's well known
that Beethoven worried his themes for years in order to shape them to his
satisfaction.

Not all his music came hard.  There's some wonderful stuff - the
arrangements of songs from the British isles for voice and piano trio -
that he wrote quickly for money.  Most of them are perfect or near-perfect
miniatures.

Steve Schwartz