What is the epic song of a group?

Smoke on the Water - Deep Purple;
Sultans of Swing (especially the Alchemy live version) - Dire Straits;
Whole lotta Rosie - AC/DC; 
Psycho Killer - Talking Heads;
Contentores - Xutos&Pontapés;
Chiclete - Táxi. 

Janis Joplin "Me & Bobby McGee"
Aretha Franklin "Respect"
Bill Withers "Use Me"
Otis Redding.... the above....
Isaac Hayes "Theme from Shaft"
Peter Frampton "Do You Feel Like We Do"
Peter Gabriel "Sledgehammer"
T Rex "Bang a Gong"
Mountain "Mississippi Queen"
Ram Jam  "Black Betty"

I decided to forgo the major artists that have decades of output. (Where do you start?)

Private Sorrow/Balloon Burning - Pretty Things 

Obviously Bohemian Rhapsody by Queen possibly the best known Epic group song of all.

A Day in the Life works fine for me for The Beatles as well. I’d also take Twist and Shout.

Echoes by Pink Floyd.

Graceland by Paul Simon

Suspicious Minds by Elvis

What’s Up? 4 Non Blondes

Dream On Aerosmithh

Back to Black - Amy Winehouse

Ramblin Man Allman Brothers

Just Between You and Me - April Wine