What is the epic song of a group?

My choice for another epic song would be Baba O'Reilly (aka Teenage Wasteland) by the Who. Builds slow and builds and builds till a feverish ending. Great lyrics. Epic

Ahhh here is another one. Yes "Close to the Edge" Elements of different intensties and moods. I hear several epic parts of this masterpiece. The organ and guitar solo near the middle and Jon Anderson's emotional ending. "Epic"

Iron Butterfly: In-A-Gadda-Da-Vida
Steely Dan: Hey Nineteen
Wishbone Ash: Throw Down the Sword
Yes: Starship Trooper
Allman Brothers: Whipping Post
Janis Joplin/Big Brother: Summertime

King Crimson - Court of the Crimson King AND Starless.
Yes - Close to the Edge.
Rush - 2112.
Pink Floyd - Us and Them.
Van Der Graaf Generator - A Plague of the Lighthouse Keepers.
Can - Halleluhwah.
WAR - The World is a Ghetto.
Genesis - Suppers Ready.
Lynyrd Skynyrd - Free Bird.
Mike Oldfield - Tubular Bells.
Roxy Music - Avalon.
Henry Cow - Living in the Heart of the Beast.
Zappa - Way too many to list.....

Epic... in terms of production, sound quality, songs, etc... I'd vote for two Supertramp albums:  Crime of the Century of course, but also the less appreciated (post-Hodgson) Brother Where You Bound.  Several tracks are a musical journey, and reference quality sound production.  I've heard 3 different CD pressings of "Brother" over the years, and my first edition CD from 1985 is still the most dynamic.  Get it if you can!