What makes someone a great artist? Surely one of the criteria has to be to what extent they have revolutionised their art form. On that measure alone the trumpeter Miles Davis must be regarded as one of the most innovative and creative musicians of the 20th century.
At the age of 18 he played an important part in the musical revolution called bebop. Throughout his 50-year career he released many outstanding records but in 1959 he surpassed any of his previous work with the release of Kind of Blue. Modal jazz was born. Again in 1970 Davis released another era-defining and path-breaking album Bitches Brew (that Davis used the sexist word "bitch" in the title, as a term for excellence, clearly taints the album).
No wonder Davis was called the "Picasso of jazz". Not only did he create wonderful abstract music, but he also constantly pushed back musical boundaries. Even with his last studio album, Doo Bop, recorded when he was as old as your average grandad, he was fusing hip hop with jazz.
This anniversary of Bitches Brew has seen the release of a sumptuous box set, which includes masses of unreleased material, live versions and other ephemeral goodies. Priced at £50, it's more of a luxury gift than an essential buy. But don't worry if you can't afford the box set: the basic CD is available for £10 and you can also download it for £8.49.
Bitches Brew had a seismic impact on jazz and rock. Davis deployed up to three electric pianos, two bassists (one playing bass guitar, the other double bass), two or three drummers, a percussionist and electric guitar, all playing at the same time.
The result was a complete rejection of traditional jazz rhythms. Instead a looser, rock-influenced and improvisational style of playing was developed.
Many jazz lovers hated the album and still do. Music critics were outraged. Davis had "sold out", they cried, and the reviewer from the biggest jazz magazine in the US claimed this was not even music.
Both Charlie Parker and John Coltrane had the same abuse thrown at them by critics. And just like Parker and Coltrane, Davis's accusers were all white defenders of "jazz purism" and would all later revise their opinions and claim that they didn't understand the music!
Throughout his life Davis worked with the most talented young musicians. He fed off their energy and creativity. The musicians whose careers were launched playing in Davis's bands read like a who's who of jazz - John Coltrane, Bill Evans, Herbie Hancock and Wayne Shorter, to name a very few.
For sure, the late 1960s produced some fantastic jazz music, but record sales were low and even Davis was performing to half empty clubs. At the same time rock festivals were drawing in huge crowds - this was the era of Woodstock and the rise of counterculture.
It was a time when US society was being torn apart by the Vietnam War. The civil rights movement in the US South had turned into the fight for Black Power and a string of urban uprisings shook northern US cities. Huge numbers of young people were being radicalised.
Davis consciously decided to change musical direction. He told his biographer, "I started realising that most rock musicians didn't know anything about music, couldn't read it, couldn't even play different styles...but they were giving the public a sound they like." In his usual modest way he added, "I could do all that and much better." Davis became a jazz-rock star and he was responsible for the development of the jazz-fusion/jazz-rock style, which became hugely popular in the 1970s. He had joined the Woodstock generation. Gone were the sharp suits and on went the hippy clothes and urban street wear.
But was Davis political, I hear you ask. The truth is, he did do occasional benefits for progressive causes, but he was no Max Roach. But from the age of 18 to the day he died Davis was a rebel. His aura was that of the consummate hipster - a person who hated the police, an artist who demanded respect in a period when racism polluted the world of music. Every time I saw Davis perform, he played with his back to the audience. This angered some people who thought he was arrogant or even a reverse racist.
When a friend of mine asked him why he played this way he replied, "Nobody ever asks classical orchestra conductors why they have their backs to the audience. The reason is that they're telling the orchestra what to play and when. You don't criticise them for doing it, so why do you criticise me for doing the very same thing?"
Just like his music Miles Davis was always sharp.