What is the epic song of a group?


I will start. I vote for Stairway to Heaven for Zep. Its grand with a great finish. I will throw in Salisbury by Uriah Heap. Ok lets see some posts of what you think is a groups masterpiece.
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Purple Haze - Jimi Hendrix                            Dark Star - Grateful Dead                              Satisfaction - Rolling Stones                        God Save The Queen - Sex Pistols              Horses - Patti Smith                                      White Room - Cream                                      A Salty Dog - Procul Harum                           Eight Miles High - the Byrd's                          Stolen Moments - Oliver Nelson
Miles Runs The Voodoo Down - Miles Davis                                                                  The Unknown Soldier - Weather Report      A Love Supreme - John Coltrane
The Doors - Light my Fire.
The Cream - Sunshine of your Love.
The Who - Won't get fooled Again.
The Doors - Light my Fire.

+1.  The full 7 minute version, of course, featuring the amazing keyboard work of the late Ray Manzarek.

Regards,
-- Al 
Robin Trower - Too Rolling Stoned
ACDC - The Jack
Zappa, that twisted genius reinvented himself so many times who the hell knows.
Perfect Alice Cooper tune.  Alice himself said that was the song he most identified with.  
Lady Fantasy - Camel
Gates of Delerium - Yes
Question - The Moody Blues
Karn Evil 9 - ELP
Nine Feet Underground - Caravan
I Walk the Line- Johnny Cash
Ripple - Grateful Dead
Free Bird - Lynyrd Skynyrd. 
Summer of 69 - Brian Adams
Jungleland - Bruce Springsteen
Living on a Prayer - Bon Jovi
Abbey Road Medley - The Beatles
Someone Saved My Life Tonight - Elton John
Italian Restaurant - Billy Joel
Suppers Ready - Genesis
I'd Love to Save the World - Ten Years After
Desolation Row - Bob Dylan


Tomorrow Never Knows or simply Revolver - Beatles
Mellow Yellow- Donovan
Suite Judy Blue Eyes - CSN
Brownsville Station "Smokin’ in the Boy’s Room"
REO Speedwagon "Ridin’ the Storm Out"
Kansas "Dust in the Wind"
Jackson Browne should be "These Days" but probably "Running on Empty"
Gregg Allman "Midnight Rider"
Thin Lizzy "Johnny the Fox"
Warren Zevon "Warewolves of London"
Foghat "Slow Ride"
Eric Clapton "Layla"
Steely Dan "Reelin’ in the Years"
Doobie Brothers "Jesus is Just Alright"
Neil Young.. simply because of radio play "Southern Man" or "Old Man"
America "Ventura Highway"
Joe Cocker "With a Little Help From my Friends"
Sweet "Ballroom Blitz"
Sniff n’ the Tears "Driver’s Seat"
Walter Egan "Magnet & Steel"
Dire Straits because of MTV "Money for Nothing"
Pink Floyd "Money"
Bob Seger "Night Moves"
Grand Funk  "We're An American Band"






With the Beatles there are a lot of songs to chose from. In my choice of Tomorrow Never Knows placed last  on Revolver though it was the first recorded ushered in a new chapter , I guess the last chapter,  which in my mind made it more epic. 
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?)




Post removed 
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
Cake  "Short Skirt, Long Jacket"
Aldo Nova  "Subject's Theme"
Night Ranger  "Sister Christian"
Black Sabbath  "Iron Man"
Van Halen  "Jamie's Crying"
Roy Orbison  "Cry'n"
Ringo Starr  "Photograph"
George Harrison  "While my Guitar Gently Weeps"


You Really Got Me - The Kinks

I need to stop these songs are popping in me head in no particular order. 
Another example would be "Eruption" by Focus. "Warning" by Black Sabbath. "Fire on High" by ELO. "2112" by Rush."Funeral for a Friend" by Elton John. "Close to the Edge" by Yes. 

The Beach Boys: "God Only Knows", written by Brian Wilson.

Jimmy Ruffin: "What Becomes Of The Broken Hearted", written by William Weatherspoon, Paul Riser, and James Dean.

The Band: "The Weight", written by J.R. Robertson.

The above are by far the most "majestic" Pop songs I’ve ever heard, on a par with Beethoven.

Bob Dylan: "Like A Rolling Stone", written by Robert Zimmerman.

Skeeter Davis: "The End Of The World", written by Arthur Kent and Sylvia Dee.

Tom T. Hall: "That’s How I Got To Memphis", written by TTH. Also done really well by Buddy Miller.

John Hiatt: "Lipstick Sunset", written by JH.

Lucinda Williams: "West", written by LW.

Richard Thompson: "Shoot Out The Lights", written by RT.

Television: "Marquee Moon", written by Tom Verlaine.

The Beatles: "Strawberry Fields Forever", written by John Lennon.

The Beatles: "A Day In The Life", written by John Lennon and Paul McCartney.

The Dwight Twilley Band: "I’m On Fire", written by DT.

Emitt Rhodes: "Fresh As A Daisy", written by ER.

Nick Lowe: "(What's So Funny 'Bout) Peace Love And Understanding", written by Declan Macmanus.

Since we appear to be deviating from the criterion of "groups" that was stated in the OP, I’ll add the following to my previous response:

"Both Sides Now" -- Judy Collins (written by Joni Mitchell, of course)
(The original version, that was included in Judy's 1967 "Wildflowers" album and was released as a single in 1968, not the disappointing later version that is sometimes heard).

A masterpiece, IMO.

Regards,
-- Al
Al, speaking for myself, that’s because very few groups have a member capable of writing what I consider a song, let alone an epic one ;-). By the way, though I don't care for Joni (to put it mildly), I agree with you about Judy’s version of "Both Sides Now" ---Eric.
War - All Day Music
Johnny Guitar Watson - A Real Mother For You
Bruce Hornsby - The Way It Is
Elton John - Levon
Randy Crawford - Knockin' On Heaven's Door
Stanley Clarke - East River Drive
Brad Mehldau - Since I Fell For You
The Crusaders - Hard Times

Gene Clark - Strength of Strings
Pink Floyd - Echoes
Neil Young - Cortez the Killer
Elton John, “Burn Down the Mission”
Billy Joel, “We Didn’t Start the Fire”
and +1 for the Beatles, “A Day In The Life”


In no particular order....
Eagles - Hotel California
Molly Hatchet- Gator Country
Skynyrd- Free Bird
Patsy Cline - Crazy
Paul Simon - Late in the Evening
Frank Sinatra - That's Life
David Bromberg - Cocaine Blues
Linda Ronstadt - Long Long Time
Stuff - Do You Want Some of This?
Doc Watson - Sadie
Eris Clapton - Layla
New Grass Revival - Lee Highway Blues
Bobby Bland - Stormy Monday Blues
Temptations - My Girl
Wilson Pickett - Mustang Sally
Elton John- Take Me to the Pilot

I now realize many of us, certainly I, didn't take the "epic" qualifier seriously enough in our nominations.
Talking Heads-Burning Down the HouseEagles-DesperadoRolling Stones-Ruby TuesdayBob Dylan-Lay Lady Lay
Jethro Tull-Locomotive BreathPink Floyd-Us and ThemBeatles-Let It BeElvis-Jailhouse RockMoody Blues-Nights in White SatinSimon and Garfunkel-Scarborough FairPeter, Paul and Mary-Blowin' in the WindMamas and Papas-California Dreamin'Cars-DriveHeart-Crazy on YouPrince-When Doves CryDire Straights-Brothers in ArmsJudy Collins-Amazing GraceAretha-ThinkLinda Ronstadt-Rock Me on the WaterSteely Dan-Rickie Don't Lose That Number
Supertramp - School, Breakfast in America, Crime of the Century
Beatles - Yesterday, Hey Jude
Neil Young - Heart of Gold
Bruce Springsteen - Born in the USA, Tougher than the rest
Joe Cocker - Up where we belong
Stanley Clark - Vulcan Princess

Some more goodies for you....
Sara - Bob Dylan
Lightnin strikes - Lou Christie
Cheryl's goin home - Bob Lind
On Saturday afternoons in 1963 - Rickie Lee Jones
Monday Monday - Mamas and Papas
Thats Right - Neil Christian
Elouise - Barry Ryan
Stuck inside of mobile with the memphis blues again - Bob Dylan
djones51 -
Appreciate the explanation for your choice of Tomorrow Never Knows as The Beatles’ epic. Revolver and that track in particular certainly announced a "new direction" they were taking
It isn't their best or most memorable song maybe 'epic' isn't the right catagory perhaps song that redefined a group or introduced something new. The wiki page on the song  is an interesting read. 
OK what about The Rolling Stones and Goin' home from Aftermath UK version of course
Ten Years After’s I’m Going Home at Woodstock is even more epic coming in at 11:24 on Youtube. Maybe the most epic of them all. Excellent sound quality. Headphones are recommended.

https://youtu.be/bW5M5xljdCI

My personal Musings on the subject.....
+1 for Genesis, Suppers ReadyProcol Harum, Whiter shade of PaleSmall Faces, Itchykoo ParkThe Rolling Stones, Finger Print FilePatti Smith Group, WaveTodd Rundgren, Parallel LinesPink Floyd......Ok, everything they did.Traffic, Dear Mr. Fantasy (I know some will argue Low Spark but I dig Mr. Fantasy)Adrian Belew, I am what I amKing Crimson.....(Ok, lets not even go there at trying to guess.)Yes, "Siberian KhatruNeil Young, Old Man or A Man Needs a Maid or Cortez.....you pick.Andrew Newton, His version of Hallelujah (best I ever heard anywhere by anyone. Ever!)Genesis, Seven Stones.....wait, I already chose....Van Morrison......(all he has to do is open his mouth and it’s epic)Mark Knopfler, (see Van Morrison above but add guitar)Santana, Soul Sacrifice Live at Woodstock https://www.youtube.com/watch?v=AqZceAQSJvc
Speaking of Woodstock: Joni Mitchell, Woodstock performed live, what a voice! https://www.youtube.com/watch?v=3aOGnVKWbwcSpeaking of voices, the woman with the four octave voice.....Phoebe Snow, https://www.youtube.com/watch?v=7OxTVxGhHFMAllman Brothers Band, Melissa.....love this acoustic version https://www.youtube.com/watch?v=ggeab0lKz2c
Natalie Merchant, Um, well, if I had to choose then (hand over my eyes) Gulf of ArabyTori Amos, IciclesELO, Can’t get it out of my HeadThe Band, of course, The Weightetc.....etc.....etc.....





I'm disappointed to see members mentioning not necessarily the most epic songs by a band, but rather the old, most popular hits that everyone knows by heart.
I must agree with OP concerning Deep Purple and Child in Time. I think that would be their high water mark. Let's see, what else...

Sway - Rolling Stones
November Spawned a Monster - Morrissey 
Accidentally Like a Martyr - Warren Zevon
Precious - The Pretenders
I've Returned - Squeeze
Junkhead - Alice In Chains
Street Life - Roxy Music
It's Over - Level 42
Untogether - Lush
Adam and Eve - October Project

I could think of a million more, but these are the first to come to mind.