OK musicians and plain ol' music lovers, post up the ONE song that you would pick if it were the only one you could ever listen to again. No "this or maybe that" in this thread. Pick one song. I'll start.
I first discovered Rush in about 1983 and started slowly collecting their catalog. (I was young with no job and records were expensive.) When I finally got my hands on a copy of their album Hemispheres in 1987, it blew me away. The first track on the album, Cygnus X-1: Book Two (Hemispheres) immediately became my favorite song and it remains so today, 30+ years later.
This song has it all: Hard rock, amazing musicianship, over the top lyrics about gods fighting for control of man's destiny, odd time signatures, key changes... the modulation back to the original key that begins at 15:44 and concludes at 15:50 still gives me chills. Oh yeah, and it's 18 minutes long!
Here's a great link to the song with an excellent fan-made comic book. Enjoy!
Braaapin' aint easy.