It was New Year's Eve, 1912, in New Orleans. Louis Armstrong was 11 years old. He had set out to sing on street corners with his three buddies, hoping to earn a few nickels to help his deserted mother, Mayann, pay the bills. Later in life Louis claimed the same economic necessity may even have forced his mother to turn to prostitution, or "hustling" as he called it, adding, "if she was, she certainly kept it out of sight". But back on December 31st, 1912, all that concerned him was the fact that one of his "stepfathers" had left a .38 in the Armstrong home in the notorious red-light district of Storyville and near midnight, as was the custom in New Orleans, Louis shot that pistol high into the night sky. But his sense of delight soon gave way to terror.

"I had just finished firing my last blank cartridge when a couple of strong arms came from behind me," he once wrote. "I broke out into a cold sweat. My companions cut out and left me, and I turned to see a tall, white detective. I started crying and making all kinds of excuses: `Please mister, don't arrest me. I won't do it no more. Please. Let me go back to mama'."

However, his cries were ignored by detective Edward Holyland. The next morning Louis Armstrong was sentenced to three years in the Home For Coloured Waifs. And that is usually where any musical history of Satchmo begins. Check the sleeve notes of The Essential Louis Armstrong CD, which proclaim: "this is where he will learn to play the trumpet; this will be the beginning of the career of the most astonishing musician and singer in the history of jazz". In fact, the Louis-discovered-music-in-remand-school claim, like so many stories surrounding the man, is "careless with the truth" - to cull a phrase from his delicious duet with Billie Holiday, My Sweet Hunk O' Trash.

Equally loosely rooted in truth is the assertion that Armstrong created "scat" singing during the 1926 recording of Heebie Jeebies when the music sheets slipped to the floor and he "instinctively" improvised a wordless vocal. Both folk-myths were repudiated in the recently-published Louis Armstrong: An Extravagant Life by Laurence Bergreen, published by Rizzoli in New York. In fact, Louis, aged seven, first learned to play the "horn" while working on a junk wagon for a local Jewish family, the Karnoffskys. The brothers Karnoffsky told the boy he made "beautiful music" and this, as Bergreen notes, "was a startling discovery, that he was capable of pleasing others, white and black, young and old, with the sound he produced by blowing his horn; it was a discovery that led to his revolutionising jazz, and by extension, American music."

So, how did Satchmo "revolutionise" jazz, American music and, by extension, the world of popular music? By "scatting", for one thing , which it now transpires Louis "got from Jews `rockin' as in `praying and swaying'." Bergreen also quotes one witness to this conversation, Phoebe Jacobs, saying, "But Louis never talked about this in public, because he feared people would assume he was making fun of Jews praying." That said, scatting was popular among New Orleans street performers as far back as the turn-of-the-century and recordings of jazz musicians singing in this style precede Heebie Jeebies. Even so, Louis Armstrong had the hit with the song and popularised scatting, directly influencing numberless neophyte crooners such as Bing Crosby.

However, Satchmo's core influence stemmed not so much from scatting as from the way he phrased, as both a singer and a trumpet player. Tony Bennett has said: "Billie Holiday, Duke Ellington, Count Basie, Frank Sinatra, Ella Fitzgerald, they're all influenced by Louis Armstrong. He's the father. Louis had a way of phrasing and if you don't sing in that phrase, it's not authentic American music. It's a tempo that's just right." Bennett didn't complete the spoken "phrase" himself - but it is arguable that Armstrong is the father, not just of jazz, but American music in the broadest possible sense. Including even classical music, where trumpet players, as Bennett also noted, "used to run out to their teachers and ask `how did this fella hit that note?' and they'd say `we don't know!' " Nowhere is that "note" more awe-inspiring than during the opening cadenza in Armstrong's 1928 recording, West End Blues which, according to Grover Sales's book, Jazz: America's Classical Music, "became jazz's Birth of A Nation, perhaps the most widely-imitated and often-played record in jazz history. The New Grove Dictionary of Jazz also notes that "it has a unity of form and feeling rare, in jazz, and was recognised immediately by the jazz community as a work of genius. It made clear once and for all that jazz was not simply music meant to accompany drinking and dancing, but harboured expressive possibilities that had hardly been explored."

In other words the real "revolution" Louis Armstrong initiated was shifting the point-of-focus from ensemble playing in jazz to solo improvisation, self-expression in the purest sense. During what the New Grove also describes as the "unbearable tension" in the single note Armstrong holds over four bars before the final chorus of West End Blues, the world got its first glimpse into the soul of Satchmo, if not the soul of jazz. And if that's not enough, this recording also contains a wordless vocal from Louis which is so lovely and lyrical it validates claims that he was heavily influenced by opera singers.

It seems incontrovertible, too, that Armstrong's improvisatory genius was at least partly inspired by drug use. Another tune he recorded around this time, Muggles, actually celebrates marijuana, given that "muggles" is a jazz word for "weed". Armstrong also reportedly preferred fellow musicians to be "stoned", while recording and even claimed that songs like West End Blues sounded different than the earliest records he made with his legendary Hot Five band, before he was introduced to marijuana, which he used for the rest of his life. Satchmo himself was certainly often "stoned" on stage, most noticeably, according to his band members, when he'd exclaim: "I'm ready, I'm ready, so help me I'm ready" and then take flight on a solo. Equally frequently, it must be said, producing reams of high-register-riffs that may have pleased audiences and helped keep Louis "high" but which, in time, became tedious to his critics.

Some commentators, including The New Grove Dictionary of Jazz, claim that after Armstrong disbanded the Hot Five in 1929 "his work from that point represents a gradual but inexorable decline". Perhaps this is true, from a jazz purist's point of view. But such sweeping statements are patently nonsense to the rest of us. Under the "guidance" of record company owner, Tommy Rockwell and, later, manager Joe Glaser, Louis did too often pander to the pop audience; but he was a populist and clearly never forgot the lesson he learned "pleasing" his original audience, the Karnovsky brothers. The release of the three-CD set, Louis Armstrong: An American Icon, which chronicles Armstrong's work from 1946 to 1968, also pretty much annihilates any accusation of "inexorable decline" and will, perhaps, lead to a much-needed reassessment of the work of Louis Armstrong.

Indeed, I'd go so far as to suggest that the spoken introduction on the version of Wonderful World Louis Armstrong recorded during his penultimate recording session, in 1970, is as true to the psyche of the man as the trumpet introduction to West End Blues. Sadly, by this stage, Satchmo had been warned that if he played trumpet again it might kill him. Nevertheless, he kept on singing right to the end. And beyond. Way beyond. When John Glenn recently climbed back inside a spaceship, he and his fellow astronauts chose a Louis Armstrong recording to accompany them on their stratospheric trip. Which one? Wonderful World, what else?

One can be sure that when Louis did play his cornet after joining the band in that Home For Coloured Waifs he never, in his most child-like dreams, could have imagined that, in time, the music would take him not just above those "prison" walls but into outer space. Obviously, no other moment in pop history better represents Sinatra's claim that "music puts wings on the human spirit." In many ways, Louis Armstrong was the human spirit, at its best, set to music.

Joe Jackson's series People Get Ready will be broadcast throughout 1999 by RTE Radio One at 10 p.m. each Friday, beginning January 8th, with a profile of Bing Crosby. Louis Armstrong will be the featured artist on January 15th.