"Epic" compositions worth giving a spin


Not concept albums, but a single LP side consisting of a work with some sort of unity/continuity.  Possibly with one or more recurring musical themes or ideas.  Could be vocal or pure instrumental and I would think in the 20-30 minute duration.  What made me think of this is "Supper's Ready," by Genesis, which I've listened to a few times recently.  It seems challenging to put together a piece that has repetition and variety such as this and I think they pulled it off nicely.  I especially like the concert version with the added visual interest of Peter Gabriel's costumes, gestures and mime routines, but for me this one works well with just the music.  Does anyone have a favorite one-side long-form piece to throw out?
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Shine On You Crazy Diamond.by Pink Floyd on Wish You Were Here.
Technically Parts I-V and VI-X are on different sides with a couple of songs sprinkled in between, but it works for me.

If sticking to the one side only theme I’ll go with Echoes from Pink Floyd’s Meddle LP.

For a live LP I’d go with Dazed and Confused by Led Zeppelin's The Song Remains The Same.
"Get Ready"- Rare Earth Live
"Gates of Delirium"- Yes
"Anesthetize" Porcupine Tree
"Utopia"- Todd Rungren's Utopia
"A Plague of Lighthouse Keepers". Van Der Graff Generator
"Remember the Future" and "A Tab in the Ocean". Nektar
"Eruption". Focus
"Close to the Edge" Yes
"Arriving Somewhere But Not Here". Porcupine Tree
"Dabsong Concerto". And "Nine Feet Underground" Caravan
"The Snow Goose" Camel
"The Magicians Birthday".  Uriah Heep
"Child in Time" and "Space Truckin"  from Deep Purple "Made in Japan"
"Tarkus" and "Karn  Evil 9" by ELP
"The Soft Parade" The Doors
"Terrapin Station". Grateful Dead
"Thick as a Brick" and Minstrel in the Gallery". Jethro Tull
"Dogs" Pink Floyd