Spirits Known and Unknown , subtitled New Vocal Frontiers, is the debut album by American jazz vocalist and percussionist Leon Thomas recorded in 1969 and released by the Flying Dutchman label.

[1][2][3][4] AllMusic reviewer Thom Jurek stated: "Leon Thomas' debut solo recording after his tenure with Pharoah Sanders is a fine one.

... Thomas' patented yodel is in fine shape here, displayed alongside his singular lyric style and scat singing trademark...

Ultimately, this is among Thomas' finest moments on vinyl, proving his versatility and accessibility to an audience who, for too long already, had associated him too closely with the avant-garde and free jazz".

[5] Critic Robert Christgau said "The subtitle, "New Vocal Frontiers," is accurate.