https://www.youtube.com/watch?v=yfV6qF03dEg&t=12

Perhaps you didn't think of classical music per se, but this is one of my favorite pieces of music, from Mahler's "Tragic" symphony, written during a rather good period of his life if memory serves. He also didn't call it "tragic himself" I believe. Just a beautiful movement that stands on its own.

BTBAM - Lay Your Ghosts to Rest

One of my favorites long tracks is «Echoes» by Pink Floyd. More than 23 minutes.

Sleep- Dopesmoker https://www.youtube.com/watch?v=WgIktZz7Aps

https://en.wikipedia.org/wiki/Jerusalem_and_Dopesmoker

Mortal Man by Kendrick Lamar. The way it ties in all the songs and explains why the album is called To Pimp a Butterfly is amazing.

Pink Floyd - Dogs

Grateful Dead - Terrapin Station

NOFX - The Decline

TOOL - Eulogy

Phish - You Enjoy Myself

Herbie Hancock - Chameleon

Just a few off the top of my head.