The ghost of jazz past catches John Morrish in unsentimental mood. Under the sheet he sees snobbery, pretention and impurity, hold on to your berets, hep cats.

Jazz is dead. And if it's not, it's certainly beginning to smell funny.

Of course, that's hardly a revolutionary proposition, given that we are now, what, 70 years away from the New Orleans stews where it all began. Seventy glorious years, you might say with some justice. But that would be to make my point. Jazz is a corpse that won't lie down. The dreadful, dreary, tail-end of a tradition that once put whole nations on their feet and now puts whole wine bars to sleep.

Nobody is going to take away my miniscule but treasured collection of jazz albums: but I could live for a long time without hearing another would-be Dixieland combo, or be-bop ensemble, or internationally-acclaimed jazz guitarist.

Stick your head round the door of a trad jazz pub and what do you hear? A bunch of people playing scales, simultaneously, then one after another, then simultaneously again.

Treat yourself to an over-priced London pizza, and have your conversation drowned by some be-boppers. What do you hear? A bunch of people playing a different set of scales (modes?) at double-speed, simultaneously, then one after the other, then simultaneously again.

Drop in at some hushed arts centre and listen to our guitarist playing scales, on several strings, then on one string, then on several strings. Applaud gently...

To adapt an old quotation, I've got nothing much against jazz except the sound it makes. And that's only part of the case against. Much worse features of jazz, in our current musical life, are its intellectual pretensions, its snobbery, its bogus doctrine of purity of style, and its thoroughgoing anti-musicality. Those pretensions first. Take an instrument like the guitar, which we all know and love. From the time you first clamp your fingers in a C shape, you are on an escalator. Up you go, through the open chords, until you find yourself on a plateau called Folk, inhabited by strangely-coiffed geriatrics called Donovan and Bob. But everybody else has climbed back on board, so you get stuck into the barre chords, and there you are in the land of rock'n'roll. You probably feel more at home there, but still the escalator beckons.

So up you go, reading the signs on the way: sixth, seventh, diminished, ninth, eleventh, thirteenth, they say, unhelpfully. And there you are, in the land of jazz, all ready to find your way into any 1940s big band that should happen to wander by. Don't hold your breath.

It's not hard to see why it should automatically be assumed that anyone who takes his or her instrument seriously will be interested in jazz. After all, if you're not, what else is there to learn? Rock is peculiarly impenetrable to traditional pedagogy (nothing to do with small boys and scoutmasters).

One alternative is classical guitar. To tell the truth, it's not really an alternative at all, given its demand for the sort of devotion that would make a Zen Buddhist blanch and run screaming from the monastery. So you go for jazz. After all, it's a mystery, and as Toyah Wilcox once told us, there's nothing like a mystery, except perhaps a mythtery. The fact that 80 per cent of today's jazz guitar sounds like nothing so much as an endless search for the shortest distance between two adjacent semitones can only add to the attraction for some.

Hence the snob appeal. I have to admit, I'm not averse to using this. If I say I'm studying the guitar, I know I'll get a lot of silly questions like, "What style?" And a lot of silly remarks like, "Wah! Ted Nugent!" If I say I'm studying Jazz Guitar, I just get cool looks expressing either admiration or profound sympathy, except from a few persistent smart-alecs who want to know when I'm going to cut two fingers off my left hand.

I'm sure this sort of thing happens to the players of other instruments too. A friend of mine gave up playing the alto saxophone when he found it committed him to a life of jazz. The whole "stylistic purity" ethos is another unfortunate consequence of messing with jazz. Sure as hell Django Reinhardt didn't worry about that: but the books will tell you he wasn't a jazz musician at all. Frankly, that's jazz's loss, not Django's. Sadly, purity of style seems to be very important to your average jazzer, although in fairness we should say that a lot of that stems from the "para-musicians" who make up the jazz audience rather than from you and I. After all, we know a good tune or a good cascade of semitones when we hear one. Which is rarely, in the case of the latter.

Frankly, I have no time for learned disputes over whether or not it is anachronistic to play a particular number in a particular style or with a particular combination of instruments. People who spend their evenings and weekends reconstructing "authenticity" would be better off labouring in a waxworks. But the waxwork school prevails. Everywhere I go I find groups of white middle-class English people pretending they are black jobbing musicians in a Chicago rent-party at some point between 1931 and 1932. It's completely bizarre and a sad indictment of the decline of our culture's confidence. (That's enough cultural analysis, Ed.)

Of course none of this would really matter if people were producing exciting music. But to spend hours trying to purify a gloriously hybrid music is utterly futile if the end product is so weak it can barely crawl out of the end of a saxophone. Which brings me back to the sound, and my fourth complaint. Jazz's anti-musicality.

What is music supposed to do? Let us leave aside for a moment the question of song, where music's impact is mediated by the words. Can we find some sort of definition of what music is supposed to do that would satisfy every musican who ever lived? No, let's narrow it down. Let's say every Western musician who ever lived.

Well (deep breath), I think it's supposed to communicate something from one human being, or one group, to another human being or group. And the way music does this, like every other art, is to set up certain norms, and then to deviate from them. But jazz today is either all norm — or all deviation.

Looking at music in the abstract, what is it made of? Well, there's the physics of it: pitch, timbre and harmony, of which the latter two are just embellishments of the first. And then there's rhythm, defined (by me) as the presence of sound or its absence and the relation between the two. But that's only in the abstract. In practice the principal quality of music is how much it resembles other music and how it deviates from that other music. This gives us things like tradition, artistry (for individuals) and construction (within individual pieces).

Going back to that primordial swamp whence jazz sprang, we find a considerable African tradition, kept alive in field hollars and the like in terms of pitch, and in proto-jazz music like Ragtime in terms of rhythm.

Here's an experiment. Pick up your guitar and find yourself a major scale, for instance at G. Now play A (the 2nd) and then Bb (minor third). Now bend that so that you get a note somewhere between Bb and B. Somewhere there is a sweet spot, a note that, in context, should be familiar to you, most likely through blues and soul rather than through jazz. It's a blue note. There's another one between F and F#.

The authorities tell us (I cite James Lincoln Collier, "The Making Of Jazz") that those notes are African. African scales, related as they are to West African languages, cannot abide the semitone. So when Western European and West African vocal music collided at the time of slavery, the resulting scales had pitches shifted about half-a-semitone at the point where a semi-tone gap would otherwise have occurred, ie at the collision of third and fourth, and seventh and octave.

Oh, I know, what I've been describing is in every poxy guitar book under the sun. Maybe so, but most of those books omit the necessity to bend up the minor third and minor seventh every time you play them — and only those notes. And they don't tell you that they actually have a correct pitch — although your ears will tell you that. And they don't tell you that the scale always, apparently, starts on the flattened seventh, then falls to the perfect fifth, then to the flattened third, and then to the root.

That odd, but oddly familiar sound is the first root of jazz. The second is the strange sound of the three-against-two rhythm, which is the root of the whole jazz rhythmic impulse, and in particular the jazz musician's freedom from the rhythm section.

Together, these things are incredibly expressive. Any early blues singer, whether in the John Lee Hooker or Bessie Smith tradition, will show that. And the first jazz players imitated the vocal music's sound. There is an incredible musical power in the way those notes pitch themselves just away from the notes of the standard major scale. The deviation from the norm is more powerful by virtue of the fineness of the deviation.

And then came the wholesale adoption of jazz idioms by entertainers and jazz's adoption of the "show tune" and the "standard". It became a music reliant upon a core of shared musical experience, upon which improvisation was built. And that's what we hear in all the best jazz records.

So where did it all go wrong? Well, somewhere along the line people began to believe that the blue notes were actually the same as the minor third and seventh. And with those pitches fixed, the only way to get some of that critical tension — the simple interference effect of two adjacent notes — was by sliding through the dreaded "passing notes".

Take a look at Mickey Baker's jazz guitar books and you'll see what I mean. Given a melody line, or an individual voice through a chord sequence, that goes, say C-D-E, Mr Baker and his friends will feel obliged to make that C-C#-D-D#-E etc. If, as they usually are, the other lines are doing the same thing, the result is a kind of harmonic semolina that just clogs everything up. The fact is, a melody is a simple line of intervals. Take all those intervals away, and replace them with uniform semitone steps, and what have you got. No, I don't know either, but I don't like it.

Then there's the repertoire: there isn't one any more, not one that makes any sense. If there was any logic, jazzers everywhere would be falling over themselves to produce hot new arrangements of, say, "We Are The World". Instead, they're all working on "Days Of Wine And Roses" or "Stairway To The Stars".

I used to think improvisation was the key to the health and vitality of popular music. Now it seems to me absolutely minimal in the great scheme of things.

Perhaps that's because of a decline in the general quality of improvisation. Certainly, I find it difficult to understand why some people think they do better making things up as they go along rather than working them out first. Of course, that's diametrically opposed to the jazz ethos as it has evolved: but plenty of early jazz musicians worked in carefully arranged forms.

One last thought, from my current guitar teacher, George Adey. He says the decline of improvisation is the result of people hearing lots of improvisation, lots of vamping, and precious few melodies. When they come to improvise, modern musicians improvise on a background of improvisation. When the jazz musicians of, say, 20 or 30 years ago, improvised, they improvised on a background of melody. And what came out? Richly melodic solos with something to communicate.

Jazz fans — it's over to you...