Bored stupid by written music? Tired of playing the same old chords in the same old order? The answer is to improvise, and you don't need to be a genius to do it.

WHILE HOLIDAYING IN France a few years ago, I met a violinist who used to play with the English Sinfonia. Always keen to try something new, I asked him if he wanted to play. He was enthusiastic, but eventually declined, explaining he couldn't perform without a written score. In other words, he was completely unable to improvise.

But what exactly does improvisation mean? What manner of unholy, complex techniques does it involve that could frighten a professional musician with rigorous training and 40 years' experience behind him?

As the renowned British guitarist Derek Bailey says in the introduction to his inventively titled book 'Improvisation': "Improvisation enjoys the curious distinction of being both the most widely practised of all musical activities, and the least acknowledged and understood."

Improvisation may be simply defined as creating, playing or singing something spontaneously. It's something virtually all pop musicians can do, regardless of experience or technical expertise. It's used as a compositional tool, and can also give life and variety to live performance.

And although improvisation is something that's often viewed as a group activity, it is actually possible to improvise alone. If you're strumming away in your bedroom, searching for that elusive hit single, you may come across a progression or rhythm you want to use as the basis of a song. You could then sit down and try to work out in detail how to improve it. The chances are, however, you will just play around with it, try a slightly different rhythm, a different chord, maybe even an inversion, and eventually find something which fits and which you're happy with. This is improvisation — even though there's nobody else involved.

Or picture this. After playing the same old set for two weeks on a tour of Cornish Miners' Welfares, you feel that although the songs are all very tight and slick, they're lacking that earlier energy and excitement. To try and liven them up, you double a note, leave a couple out, or shift the emphasis in the second bar. Whether consciously or subconsciously, you liven up the show both for yourself and for the audience.

Besides such use of improvisation as an aid to making existing music more enjoyable, it's also pursued as an end in itself. It was probably the first form of music to exist, and continues to be important throughout the world.

It is only in Western classical music that improvisation is systematically frowned upon. Here, the obsession with form and hierarchy and the near deification of The Composer tend to make anything unexpected and possibly "wrong" unacceptable. So although classical musicians can be said to be improvising in their interpretations, composing music simply is not their job.

It wasn't always so. In the Baroque period of the 17th Century, improvisation was a crucial element of the music produced by Bach and his contemporaries. Most commonly an outline of an accompaniment would be given, which was then used as a basis for improvising by the performer, using embellishments, decorations and harmonic variation. Although they may have been known before, their actual use (and non-use) on the night was entirely up to the performer.

As the Baroque style ran its course, improvisation in classical music was relegated to specific sections, rarely under the performer's ultimate control. It remains so to this day, with the consequence that many virtuoso performers cannot make up tunes as well as you or me.

Elsewhere in the world, improvisation occurs in most musical styles to varying degrees. In 20th Century Western music the biggest growth area of improvisation has been within the realm of jazz. For 40 years, jazz musicians improvised on chord changes and song structures. Leaders like Louis Armstrong, Charlie Parker and Thelonious Monk achieved landmarks which other players aspired to, and occasionally surpassed.

From the late 1950s, American players like Cecil Taylor, Ornette Coleman and Don Cherry transcended any potential limitations of form (harmonic and rhythmic structures) to "just play". They improvised freely from the barest melodic or thematic ideas, or from nothing at all. Thus was born "free jazz" - a notoriously difficult style of music, both to listen to and to play. The underlying principle that there should be no restrictions on expression is not, however, the end of the story. "Free jazz" players must be well-disciplined to realise their own limitations, and have a well developed sense of what will sound appropriate.

In Britain, free improvising took off a few years after its emergence in the States. It was originally inspired by American developments but soon found its own path. The "jazz" label was rejected and musicians tried, and often succeeded, to create a very British music. But totally free improvising was never that popular — and musicians struggled then, as now, to keep a marginalistic music alive in the face of small (but dedicated) audiences and general market apathy.

"A formal knowledge of music may help, but it can also hinder if you have too many preconceptions of what is right or wrong."

Improvising in rock music became widespread from the mid-1960s onwards. There was input from jazz, free music, and from the "Indian thing" then in vogue. The ascendancy of the LP over the single left more time and space for the development of ideas, and the use of mind-expanding drugs made performers and audiences more receptive to the unpredictability and potential "weirdness" of improvised music.

The featured improvisers at the time were guitarists and keyboard players, and their playing was rooted in the blues form. Jimi Hendrix reached heights of invention on the electric guitar which have yet to be surpassed, although his phrasing and melodic sense came straight from the blues and his use of "noise" as music had been pre-empted by the American free jazzers.

On this side of the Atlantic, "progressive" rock bands like ELP, King Crimson and Yes found success through extensive use of improvising, but became increasingly pompous and self-indulgent as virtuosity was pursued as an end in itself.

Improvising continues in pop music today. Heavy rock guitarists are the most prominent improvisers, hip-hop DJs improvise at the turntables, rappers improvise their raps. African pop features improvised solos and minimally varying rhythm parts.

Improvising in rock/pop can be called "partial" and "idiomatic". In other words, although there are spontaneously played notes and rhythms in the performance, the piece as a whole has a certain style and feel, is generally in a certain key, and has some degree of structure. Within this framework, players can make up their parts as they go along, so the song is rarely performed exactly the same way (although this is not always consciously noticed by performer or audience).

It's very difficult to give an all-embracing "how to do it" method of improvising, but certain factors are common to all improvised music — from Baroque to Indian music, Flamenco to free and, of course, pop.

First off, it's important to have a clear sense of purpose. What are you trying to achieve? The simple answer is good music. But who defines the quality of the result? Are you after audience appreciation, or the satisfaction of the performer? In the best type of improvisation, the two will coincide — but this doesn't always happen.

Usually you'll have some guidelines to work from. For example, if you're playing in a dance band you know that whatever you do, it mustn't stop people dancing. There is generally a set key to play in, and this must be borne in mind. However, within any key or chord progression there are many alternative possibilities which can change the sound of a piece without changing its basic character. Jazz players have become especially adept at exploring harmonic alternatives, but the principle is just as valid for pop. Extending chords by "superimposition" (for example, C7 becomes C9, C11, or C13) or substituting related chords (for example, F6 for Dm7) will create an interesting variation. Melodies can be embellished or changed in a number of ways: inserting or removing notes, phrasing differently with alternative stresses or rhythms.

These are all things which can be done by a single improvising player. When two or more members of a group improvise at the same time, the possibilities multiply — and so do the potential problems. The players must be aware of, and responsive to, what the others are doing, and be able to use their ears as the ultimate judge of quality.

It's all a bit like speaking. When you have a conversation with anybody, you improvise your words. Experience and education have taught you a certain stock of words and phrases from which you choose something appropriate. When somebody replies to something you've said, you in turn respond to that. Similarly, if someone in your band plays something, you play something which complements or replies to that.

The analogy can be extended further. If someone speaks to you in Swedish and you know only English, your conversation won't get very far. If someone starts talking about nuclear physics and you respond with an anecdote about deep sea fishing, the results will be of interest only to dedicated surrealists. Similarly, if you're asked to improvise an accompaniment to a slushy ballad you would not respond (hopefully) with a handful of power chords before launching into a heavily distorted riff with random feedback. (Although a dedicated surrealist might.)

"Technique and dexterity play their part, but just as important as what you can do is an awareness of what you can't."

The analogy breaks down when you realise that if a load of people all talk at once, the result is unlistenable — whereas bands do all play together, and occasionally the result is some very good music. But you get the point.

In performance, audience response plays a vital part. Everybody wants a favourable reaction, but there are inherent dangers — namely the "performing seal" syndrome. If you try something on the spur of the moment and it goes down well, there is a natural desire to try to repeat it. But this is not always possible. By the end of a gig, you may well have forgotten what you actually played. And if you can't repeat it, you could get tied up in all sorts of knots trying to track down the same notes, or even the same feel. Even if you do manage to recreate the magic moment fairly accurately, the effect can still be radically different. The other band members could decide to play something different as well, or your conscious searching might negate the spontaneous element which made it all so successful in the first place.

If you use improvisation as an aid to composition, you're doing what's known as "jamming". Anything you come upon by chance while jamming can be incorporated into the structure of a piece, but the attraction of live improvising is partly to keep music fresh and alive.

A formal knowledge of music is as unnecessary to improvisation as it is to other aspects of pop. It may help, but it can also hinder if you have too many theoretical preconceptions of what is "right" or "wrong". Again, the importance of the ear telling you what fits and what doesn't cannot be overemphasised.

Technique and dexterity play their part, but just as important as what you can do is an awareness of what you can't do. Given the spontaneous nature of improvisation, things happen quickly, and you have to know whether your fingers, arms or vocal chords will be able to translate a semi- or sub-conscious idea, instantly, into a good sound coming out of the PA.

Improvisation technique can be practised in various ways, and a lot of it is bound up in general musicianship. Practising chord changes and scales, being familiar with substitution possibilities, knowing different rhythms which all have the same feel, and generally just knowing your instrument all contribute to building up a vocabulary from which you can pick out licks and phrases which fit.

If you're practising on your own, a tape of your own or other people's music is a useful aid. Play along, adding a new part of your own. It doesn't have to be complicated (no improvisation needs to be), it just has to fit. It may be a new melody, a harmony line, a different chord, a complementary or cross rhythm... whatever. Besides improving technique, you will also develop your ear and build up a personal vocabulary.

The use of new digital technology in improvising is so far largely unexplored — because it is so new and because it was designed for a specifically non-improvising purpose.

However, the mysterious world of MIDI does present exciting opportunities. The player has to learn a new technological language, and apply it in a similarly musical way as with traditional instruments.

Sequencing may at first seem to be the exact opposite of improvising — programming a computer to repeat a pattern is hardly spontaneous. But the recall of programs can be, in the same way as recalling things from your memory.

If sequencers are to be used in improvisation, the drummer must play to the same time-keeping click-track as the patterns are programmed to. This limits the use of rubato effects (spontaneous slowing down or speeding up), and requires pretty tight drumming if the results are to sound like anything other than a mess — but it can be done.

Sampling techniques are probably easier to incorporate into improvisation. An obvious advantage is the vast range of sounds which can be employed. Again, program loading times and limited sampler memories impose restrictions, but intelligent use of variable parameters can turn a single sample into an orchestra of effects.

Whether digital technology will find widespread improvising applications remains to be seen. In the meantime, whether you use it for composition or performance, improvisation is a weapon in your musical armoury with the potential to produce truly exciting and individual results.

Use it wisely, train and trust your ear, and you'll surprise yourself — and your audience.