More mood specific than definitive but here are a few that are timeless for me:
Charles Mingus - Good By Pork Pie Hat
Bonnie Rait - Angel from Montgomery
Miles Davis - Flamenco Sketches
Joni Mitchel - Conversation
Grateful Dead - Darkstar (Date Specific)
Billie Holiday - Stars fell on Alabama
Nina Simone - Wanna Little Sugar in My Bowl
Allman Brother -In Memory of Elizabeth Reed
Van Morrison - Into the Mystic
Led Zeppelin - The Rain Song
The Who - Babba O’Riley