Quite a weird idea for a thread, but I realised last night while listening to Deadwing for the first time that I love prog so much because it's the one genre that can actually make me smile when I hear something really unexpected and amazing in a song. Some of my favourite moments are:
Opeth - The Lotus Eater - 5:53. When all the dissonance is building up right before this awesome keyboard lead started, I was expecting something like the intro to The Leper Affinity, ie just another riff to start, but when I heard this creepy, almost jazzy keyboard part it made me love this album/band even more.
Dream Theater - Learning To Live - 8:16. Another case of something you only get in prog, I love it when a band repeats melodies or references other songs from their work in some way, so when the Wait For Sleep riff started it was unexpected but great.
Transatlantic - On The Prowl - Just the whole song here wasn't what I thought I was going to be getting from The Whirlwind, so it was great when the amazing bassline started and I realised it was going to be at least mildly funky.
Porcupine Tree - Gravity Eyelids - 4:00. I've said this before, but this is some of the most menacing guitar I've ever heard, and it really caught me off guard completely.
Bonus mention: Tool - Faaip De Oiad. Having been lulled to sleep when first listening to Lateralus in bed by Disposition, when this came on I woke up and was completely terrified. This was not enjoyable.
Anyway, what are some of you guys' favourite unexpected musical moments?