One album, you got to be kidding, right?
Three is just so much. From Astral weeks, What's Goin On, Greetings From LA, There's a Riot Goin on,
To things like Tago Mago (Can) In a Silent Way (Miles) and Sextet/Six Marimbas (Reich).
To more modern stuff like Hell Among the Yearlings (Gillian Welch), Silur (Tarwater), Homogenic (Bjork) and White Chalk (PJ).
But if I absolutely had to I'd have to choose from Greatest Palace Music (Bonnie 'Prince' Billy, Sometimes I wish We Were An Eagle (Bill Callahan) and (if push comes to shove I guess at the moment it would have to be) Jukebox by Cat Power.
Why? God knows, partly because it has a sublime version of (Joni Mitchell's) Blue and Metal Heart of course. But partly because I can remember the first time I heard it and that, to me, seems like better days....