His career was one of constantly reinventing himself. How is it that Miles Davis continues to be jazz's biggest selling artist, even 15 years after his death, asks Stuart Nicholson

When trumpeter Miles Davis died on September 28th, 1991, at St Johns Hospital and Health Center in Santa Monica, California, jazz was plunged into a crisis of confidence. Its only surviving bona fide superstar was suddenly gone. "Jazz was already short of marquee names when the 1990s began," wrote the American critic Francis Davis in Atlantic Monthly. "The loss of [ Davis] threatened to become a permanent void at the top of the bill."

Although Davis had been an omnipresent figure from the time he played Hal to Charlie Parker's Hotspur in the 1940s to his final recordings with rap artist Easy Mo Bee in 1991, he dropped out of the music business between 1975 and 1981. While he passed the time dabbling in coke and sex, his career on records went on unabated as his record company Columbia delved into their vaults for previously unreleased material.

When he made his comeback concert at New York's Avery Fisher Hall on July 5th, 1981, in terms of record releases at least, it was as if he had never been away. Since his death in 1991, there's been a distinct feeling of déjà vu as sumptuously produced Davis box sets, often with previously unissued material, have continued to appear at regular intervals.

They have dominated the album charts and won Grammy awards. In 2003 The Complete Jack Johnson Sessions made it to four on the Billboard Jazz Chart, while last year, The Complete Bitches Brew Sessions went platinum. And released this month comes the latest box-set from Columbia/Legacy called The Cellar Door Sessions 1970.

By its second week of release in the US it had shot up the Billboard album charts to 16. In death, just as in life, Miles Davis remains a powerful force in jazz. Since 1996 there have been eight Miles Davis releases in the Deluxe Box Set series and they have garnered a total of eight Grammy awards.

There is no reason to suppose the new Cellar Door Sessions 1970, an elegant six CD set with its impressive booklet containing reminiscences about the sessions, colour photos and discographical information, will not do the same. Meanwhile, work has already started on a ninth box set, The Complete On The Corner Sessions. So how is it that Davis continues to be jazz's biggest selling artist 15 years after his death?

For saxophonist and arranger Bob Belden, who compiled the set with former Davis keyboard player Adam Holtzman, it's down to, "the Davis myth, Davis's musicianship, the need for heroes - even dead ones - and a reminder of better days". It's a compelling argument. After all, Davis was a survivor of jazz's Golden Era and his recorded legacy comprises some of the best-performed and most adventurously crafted albums in jazz.

His whole career was one of constantly reinventing himself by deftly changing the backdrop that framed the fragile lyricism of his playing, regular feats of musical prestidigitation that kept him ahead of the game for almost 40 years. The distinction in his music was how the varied settings he created for himself often influenced events within jazz itself.

Yet this does not fully explain the appeal Davis exerts from beyond the grave. Perhaps the answer to that comes from events during his lifetime.

When he announced his comeback concert in 1981, virtually every newspaper in the world made some reference to the event. Overnight he became the major draw in jazz and remained so until his death. Box offices around the world frequently could have sold out three and four times over for his concerts.

The reason was simple; audiences wanted to consume the aura and physical presence of one of the great and enduring legends of 20th-century music and to acknowledge a musical legend during his lifetime. The music, paradoxically, was less important than "the event".

Today, the music is now less important than the box-set. The fluffed entrances, the rehearsals and discarded takes that are included with the original album release may only be listened to once or twice in a lifetime but they do allow you to gain purchase on Davis's musical value system. From often unpromising beginnings came some of the great and enduring classics of 20th-century music. Package it all up with coffee-table appeal and the Davis myth lives on.

Each set provides reassuring evidence of Davis's stature as an artist, and while the mechanics of a classic recording may be laid bare, there are sometimes stunning revelations. While some of the Cellar Door material was used on the LP Live-Evil from 1971, it was heavily edited and shorn of the themes.

This new set contains more than three hours of newly discovered music from an important Davis band - saxophonist Gary Bartz, keyboard player Keith Jarrett, guitarist John McLaughlin, bassist Michael Henderson, drummer Jack DeJohnette and Airto on percussion - that almost went completely undocumented.

Gone was Davis's fragile lyricism of the Kind of Blue days, in its place a densely layered brew of interlocking sounds with Davis's electrified trumpet mediating the ebb and flow of the music. Keith Jarrett on keyboards shines in this hothouse of creativity delivering a constant stream of ideas that must have scared the life out of everyone present. You simply can't nail these sounds down with a convenient marketing tag, it seems to move in several directions at once.

As Bob Belden observes, "Most adventurous music today is suppressed by self-censorship. In contrast, Miles was 'reacting' to the sounds around him but 'creating' and defining his own language."

It's music that delivers an unexpected shock, telling us more about the today's jazz scene than perhaps we want to acknowledge. When Davis died in 1991, his most effusive obituaries grew noticeably ambiguous about the past 20 years of his career when he was the standard-bearer of electric jazz. This is because the American jazz mainstream - the style preferred by the majority - is based on the certainties of jazz's Golden Years of the past. As Christopher Porter, editor of America's biggest circulation jazz magazine Jazz Times, pointed out in a 2003 editorial: "The status quo in jazz is music that sounds like it was made between the 1940s and the 1960s."

Somehow a remarkable reversal of values had taken place. Davis exemplified jazz's flight from the status quo, whereas much of today's jazz is a flight back to it. That may be the source of Davis's lasting appeal. Musical taste is intimately tied to personal identity and is expressed through the deployment of other people's music.

With no shortage of takers - by the end of the year, Columbia/Legacy expect The Cellar Door Sessions 1970 to have generated between $3 million and $4 million in sales - the appeal of coffee-table friendly Davis box sets rests in how we want to be seen by others, which, like Davis, is cool and eternally hip.

When Charlie Parker died in 1955, graffiti across New York proclaimed "Bird Lives". In the musically conservative 1990s, there was no graffiti to mark the death of Davis; had there been, "Miles Smiles," after his famous 1967 album, might have been appropriate.

Miles Davis: The Cellar Door Sessions 1970 is on Columbia/Legacy