Last night I attended a concert (not staged) performance of
Ravel's "L'Enfant et les Sortileges," a one-act opera.
Ravel only composed two operas, both brief,
and both crammed with difficulties;
I think this one is the more difficult of the two.
I can just imagine what rehearsals were like:
a rehearsal pianist scrambling to keep up with the arrangement
of a fiendishly difficult orchestration;
and singers having to repeat and repeat their sung lines.
You come out of rehearsals like that
with the music partly memorized and ringing in your ears.

Then you perform it once, and poof! it's all over.