Having just listened to the M10 Purgatorio, I have to second Barry's inclusion of it in his Halloween program.
Give yourself 5 minutes: get out an M10 and listen to that Purgatorio movement.
How do we describe it, if this is possible in words?
Spooky?
Devilish?
Wandering and lost?
It's certainly one musical statement that carries an atmosphere.
Reminds me of some of what Berlioz did.
--John H