It is the third and final installment in a trilogy series of unissued archival recordings, following 2010's Valleys of Neptune and 2013's People, Hell and Angels.
Numerous album's tracks were recorded by the Band Of Gypsys, Hendrix's trio with Buddy Miles and Billy Cox.
A highlight of the new collection will be a pair of September 1969 tracks cut with guitarist Stills, including a studio recording of Joni Mitchell's anthem "Woodstock", which Crosby, Stills, Nash & Young would later record for their 1970 sophomore album "Déjà Vu".
Both Sides of the Sky sees Hendrix in collaboration with a handful of guests, including Stephen Stills, Johnny Winter, Billy Cox and Buddy Miles from the Band of Gypsys lineup, and Lonnie Youngblood, a notable saxophonist known for working frequently with Hendrix and was his bandmate in Curtis Knight & the Squires. "This is too f*cking incredible", Kramer said in a release.
Band of Gypsys - which before Hendrix's September 1970 death was heard exclusively on their eponymous 1970 live album - is represented by 1969 studio recordings of Muddy Waters' "Mannish Boy" and the Hendrix original "Lover Man". He continues: "It's an incredible thing".
"Jimi is just rocking it", he added. "There's never been another Jimi Hendrix, at least in my mind".
Kramer also revealed there is new live footage of Hendrix, which they plan to release in the future. Engineer Eddie Kramer - who worked on every Hendrix project before the guitar legend's death - co-produced the album with John McDermott and Hendrix's sister, Janie Hendrix. "The brain kicks off the thought process - it goes through his brain through his heart and through his hands and onto the guitar, and it's a seamless process", Kramer said.