IMAGINE A COMPUTER PROGRAM that opened up the cases of modern synthesizers and samplers, took out all the mysterious gadgetry inside, and displayed it on-screen for all to see. And imagine that as well as letting you see all those hi-tech components, the program also let you play about with them to your heart's content, creating new sounds as you went. And imagine, finally, that the program also let you transfer those new systems and sounds to other musical instruments, so that you could play them and record them.

It sounds like we're in the realms of fantasy here, but this program is very much part of the real world. It's called Turbosynth, it's here now, and if you have access to the relevant machinery, you can start making it work for you for less than £250.

The program comes from Digidesign, an established Californian software house with a long history of producing useful and inventive music software packages. Most of these revolve around the Apple Macintosh computer and various models of professional-quality digital samplers - machines like the Ensoniq Mirage, Akai S900 and Casio FZ1. Now, this sort of hardware is not cheap: a Mac will set you back at least a grand for a secondhand example, and even that may not have a big enough memory to run Turbosynth; a suitable sampler will involve a similar outlay (slightly less if you go for a downmarket model such as the Akai X7000 or Roland S220); and you'll also need a MIDI interface so that the computer can "talk" to the sampler (£350-400). Hardly paper-round stuff.

However, you may be lucky enough to have parents (or friends who have parents) who use some or all of this equipment for work. More likely, you could find that a school or college near you has invested in this gear for use with the new GCSE and BTEC exam courses in Music and Musical Technology.

Once you've got hold of the hardware, that's virtually all the difficult work out of the way - because using Turbosynth is easier than putting five past a Halifax Town team reduced to nine men.

Turbosynth takes all the component parts of a sound, sorts them into "building blocks", and displays them on the computer screen as just that - little graphic squares with pictures in them so that you can tell what they are.

There are a number of different kinds of building blocks, or "modules" as Turbosynth calls them. If you want to start building a sound from scratch, you start with the Oscillator module, within which there are a number of different preset waveforms which determine the sound's basic character; you can also have a go at drawing your own waveforms. If you're taking a sound from an external sampler, you go to the Sample module, which also offers a number of editing options so you can change the length of the sound, loop it round and round, and so on.

With the help of an on-screen tool known as the Patch Cord (a throwback to the days of big analogue synthesizers when modules had to be linked together with bits of wire), you can join up as many Oscillators and Samples as you like to form the basis of your new sound. It's just a matter of putting the graphic boxes on screen and drawing a line between them.

As anyone who's ever tried programming a synthesizer will tell you, after sound creation comes sound modification, and Turbosynth lets you modify your sound in a number of different ways. There simply isn't space here to list all the modifying options, but the modules involved include Filter and Amplifier "Envelopes" (for adjusting the time it takes the sound to start up, continue, and then die away); a Delay module (just think of it as an onscreen version of an ordinary digital delay line); a Pitch Shifter (which, er, shifts the pitch of the sound); a Modulator (which mixes one sound with another); and a Waveshaper. Believe it or not, most of these modules are familiar territory to synth and sampler programmers, and using them is a lot simpler than you might think. Less conventional (though no trickier to use) is the Stretcher, which lengthens any input you care to, well, put in.

The two most vital blocks are the ones at the bottom of the pile: the Mixer module (for adjusting the balance between different source modules) and the Output Jack, which is simply a graphic version of a jack plug and which must be inserted at the bottom of each system for the sound to be heard.

Having fun with Turbosynth is easier than it is with most music software. After a couple of hours, you realise that creating new sounds is a bit like building a wall out of Lego: every module can be linked to any other, and if you don't like the way it's fitting together, you just smash it up and start all over again - and there's no harm done.

Creating sounds that aren't completely unlistenable isn't so easy. But there's a disk of sample files supplied with Turbosynth, which you could always use as a starting point for editing. And the manual is consistently clear and helpful: an education in itself.

Speaking of which, education is probably Turbosynth's strongest application. I know of no other computer program that makes learning about sound such an entertaining pastime. So put that text-book away, check out the screen, and start Turbocharging.

DIGIDESIGN TURBOSYNTH SOFTWARE: £235 inc VAT

INFO: Evenlode Soundworks, (Contact Details)