Even the most devoted Jimi Hendrix acolyte should be skeptical by now: How much more can possibly remain in the vault nearly five decades after his passing, and even if there’s stuff squirreled away, could any of it possibly be worth hearing? Amazingly, Both Sides of the Sky is both a historically valuable document—10 of its 13 tracks are previously unreleased—and a treat musically. Consisting of random tracks recorded between early 1968 and early 1970, it serves as the third entry in a trilogy of posthumous anthologies that began with 2010’s Valleys of Neptune and continued with People, Hell and Angels in 2013. This time, cuts featuring members of both the original Jimi Hendrix Experience (bassist Noel Redding and drummer Mitch Mitchell) and Band of Gypsys (drummer Buddy Miles and bassist Billy Cox) are included, and there are several high-profile guests like fellow guitar heroes Stephen Stills and Johnny Winter. One of the most intriguing finds is surely “Woodstock,” the Joni Mitchell-penned homage to the festival she never attended. Although Crosby, Stills, Nash & Young would soon release the definitive version on their Déjà Vu album, the similar arrangement here is nothing short of exhilarating: With Miles on drums and Stills playing the organ, it’s a solid, pounding cut that shows the tune still taking shape but on its way to becoming a bonafide rock classic. He remains on the organ for another Stills written-and-sung track, “$20 Fine,” with Mitchell taking the drum stool and Duane Hitchings of the Buddy Miles Express on piano. There’s plenty of blues on Both Sides of the Sky too, a reminder that, while he loved to experiment in the studio, Hendrix was also quite comfortable peeling out stellar blues sans ornamentation. “Mannish Boy,” the Muddy Waters staple, opens the set, but it’s the back-to-back “Things I Used to Do,” a Guitar Slim number featuring Cox, Winter and CSNY drummer Dallas Taylor, and “Georgia Blues,” with a vocal by Lonnie Youngblood, that best showcase Hendrix’s ripping blues technique and once again pose the question of where he might have gone had he stuck around longer. Previously unreleased variations of familiar Hendrix vehicles like “Lover Man” and “Hear My Train a Comin’” don’t offer significant recasts of those tunes, but considering that much of this set has been gathering dust all these years (bootlegs aside), they’re remarkable additions to the official canon.