At least, that's the view of Janie Hendrix, the electric guitar revolutionary's half-sister and custodian of a vast stash of unreleased material that - further legal challenges permitting - will arrive like a strategic meteor shower over the next 10 years. ''I think this album really gives people an insight into what Jimi was doing after he finished [the last record released in his lifetime] Electric Ladyland,'' she says. ''It's really deep into the blues. It gives you a new perspective on what he was evolving into.''

Valleys of Neptune is mostly radically different versions of known Hendrix songs. His four-month studio stint in early 1969 documents a period of creative flux, bridging his last recordings with the Jimi Hendrix Experience and the first with future Band of Gypsys bassist Billy Cox. ''He was really excited about creating a new sound, bringing new music to people,'' Janie says. ''He told my dad, 'You will be doubly proud of me after this. Music is going to be so different to what we've been accustomed to.' He was in a really great mindset as far as creation.'' According to Janie, who was just five years old when her superstar brother died in London on September 18, 1970, Valleys of Neptune is just the tip of ''a mountain'' of unreleased material being prepared for issue under the Experience Hendrix LLC banner.

''I know the releases we have in store for you will be enlightening,'' she says. ''I don't think there will be anybody who will be disappointed.'' For fans of an often-mishandled legacy, that's cause for cautious optimism.

At the time of his death at 27, the Seattle-born rock god's business affairs were in such a fragmented state that shoddily edited live albums and contractually compromised compilations would far outweigh the gems found over the next two decades. It wasn't until 1995 that Janie and her father, the late Al Hendrix, gained control. They aimed a careful course through the archives by hiring Hendrix's original engineer, Eddie Kramer, to prepare First Rays of the New Rising Sun, a definitive version of the oft-pilfered album that was nearing completion when the guitarist died. But after just one more release, the rarities collection South Saturn Delta, ill health and legal dramas stalled momentum. Al died in 2002 and Jimi's brother Leon challenged Janie's authority over the estate. With that suit settled in her favour, the floodgates are set to open in a marketing pattern increasingly familiar to the nostalgic consumer.

In coming months, enhanced reissues of all three original Hendrix albums - Are You Experienced, Axis: Bold as Love and Electric Ladyland - will each feature a mini-documentary by Bob Smeaton, who did the same for the Beatles' remasters last year. This Christmas will also see a computer game in the Rock Band series. Then there's a Royal Albert Hall DVD, which, Janie says, ''is kind of reality TV as we know it today, where Jimi is followed around by six cameras for a month, on and off trains and planes and automobiles and performing at the Royal Albert Hall; in a speakeasy; in his apartment. It's Jimi as himself, kind of a day in the life from 1969.'' Perhaps the jewel in the collection is the legendary Black Gold LP - 16 acoustic demos for an autobiographical concept album Hendrix recorded in his Greenwich Village apartment in early 1970. Janie confirms the master tapes were held by Experience drummer Mitch Mitchell until his death in 2008 and will be released this decade.

''We also have the Anthology project, which is Jimi's spoken word, in audio and video form. People often say, 'What would Jimi think?' Or, 'What would Jimi say?' Well, in his words, now you will know. At least, you'll know what he's saying,'' she adds, with a laugh. ''You may not know what he's thinking.'' Indeed, the question of what Jimi might be thinking was often unclear when he was alive. His acid-spiked stage banter remains the stuff of eternal conundrum. ''That's what happens when Earth f---s with space. Never forget that,'' he warned one bemused New York audience while hastily terminating one of his last gigs. The question of what he might think today, as others compile, tweak and package the jams he never considered ready for public consumption, directly addresses the sanctity of a famously obsessive spirit.

Hendrix was one of the first stars to fully appreciate the possibilities of multi-track stereo recording and to insist on total control over the process. His perfectionism partly explains the two-year absence of studio releases between Electric Ladyland and his death. His wrangles with frustrated managers and band members over his singular vision perhaps explain the rest - although Janie bristles at the suggestion that his drug intake may also have fuelled an underlying artistic confusion. ''Jimi definitely experimented but the amount of material that is left behind is not that of an acute or abusive drug user,'' she says. ''It's that of a very creative and innovative person. Here we are, four decades later, and we're still bringing you music as fresh and vital as if it were created this month.

''So yes, there were times that he experimented but he also had a great work ethic and he utilised his clear-mind time to create music. Lots of music.'' Despite what could only have been a brief and sporadic relationship with her brother, Janie's affection for Jimi is obvious. She recalls a happy, playful, sometimes mischievous man who loved to watch cartoons while playing along on his ever-present guitar. He was soft spoken, deep thinking, politically aware and, towards the end of his life, increasingly family-oriented. ''He actually asked my dad to be his manager,'' Janie says. ''My dad said, 'I don't know anything about being a manager'. But really, he just wanted the family close, to feel a little security, to be taken care of. Because not everybody was always looking after his best interests.''

This observation has a slightly sinister resonance given the conspiracy theories that arose in the wake of Hendrix's death. Officially, he choked on his vomit in the Notting Hill flat of his girlfriend Monika Dannemann after combining sleeping pills and wine. But both she and Hendrix's manager Michael Jeffrey have been accused of foul play by various sources. While Janie Hendrix can never prove or disprove any such allegations, she says she has made peace with the unknown.

''All through my growing up, since Jimi passed, I remember people would come to my dad and say, 'How do you know somebody didn't kill him?' That really troubled my dad. Watching what he went through at those times was really heartbreaking. ''What my dad said to me was, 'You know, we could drive ourselves crazy trying to figure out if this is true; if there was a conspiracy'. ''But my dad said something very profound. He said, 'We can't bring him back but his music is his soul that continues to live on'.''

Valleys of Neptune is out today through Sony.