One of the more impressive exhibits at the recent British Music Fair didn't really exist at all. Well, that's something of an exaggeration. Let's say it existed as long as the power to the computer and monitor stayed on. Yes, you guessed it, we're talking about software; that strange collection of magnetic impulses on tape which magically converts to a useful musical tool when fed to a bunch of idle silicon chips.

Siel, the Italian company, had several packages on display, and we took a closer look at them once the Hotel Russell had closed its doors.

First there's a straightforward, real time, polyphonic sequencer which costs £22 on cassette, but is intended as an 'included with' offer when you buy the £99 MIDI interface box (three outs, two ins and a through, plus sockets to fit a Spectrum and Commodore 64). The interface is identical to the Jellinghaus box, marketed by Rosetti, which was reviewed in August's One Two.

Very simple. Once running the program will start recording the instant you hit the first note on the keyboard and will remember all polyphonic information (limited only by how many notes your synth can produce at once) plus dynamics, plus program changes. You have to tap the stop button in rhythm if you later want to loop the sequence (or 'refrain' as Siel term it) otherwise you'll pick up an unwanted silent space.

The readout shows the percentage of memory you've used and on average (a very dubious term) Siel give it a maximum running time of 20-30 minutes on a Spectrum. No editing, no chaining, one sequence only. There's a stop footpedal on the way and if you haven't used all the available voices in the synth, you can play along with the spare ones, remembering that the computer will always have priority.

Next the programmer program. This is primarily designed for the Siel Expander (One Two, May issue, page 87) which has all the sound generation circuitry of the Siel Opera 6 keyboard, and 95 memories, but no controls.

Now this £53.50 job produces one of the clearest graphic representations of a synth panel I've seen. It draws four sections on the screen — LFO, DCO, VCF, ADSR — each light blue on a dark blue background. Control knobs are black with white figures in the centre to show the value of their settings — 0-255, an unusually fine and subtle division. Imaginary 'LEDs' will glow red when switches are on.

To set in motion you first make the normal MIDI connections with the Expander and press 95 on the Expander's selector buttons. That opens the memory bank and allows the machines to communicate. Then choose a patch you want to edit and call it up twice — once to bring it up on the Siel, again to transfer the information to the computer.

The programmer is strong on assistance. If you ask for 'help', several pages of text will unfold below the front panel graphics, explaining what each of the synth controls do. Choose a department, say, LFO, and you'll get a close up of that section. And (this is the smartest bit) home in on the control you want to alter and the rest of the graphic panel will turn to a darker blue, leaving the desired control beaming out on its own light blue square. T increases the setting value, R decreases it, Cap Shift will move you around in steps of ten. The white figures change AND a small black indicator whizzes around the outside of the control knob, acting as a pointer. Gimmicks, I love 'em.

The program has a monophonic and a chord sequence built-in so you can hear what changes have been made without having a keyboard to hand. Proving Siel's attention to detail, the mono sequence covers a good four octaves so you can tell if the keyboard tracking on the filter is working. You can jump back to the old settings to compare, and if you like what you've done then dump it into the Expander permanently.

And so to Step Time, ah, who can resist its wondrous charms? This next piece of software is for the serious composer who prefers to load in his music with mathematical precision and infinite opportunity for revision. He may not even have a keyboard. He may not know what a keyboard is. As long as he's got a set of MIDI synth circuits (Siel Expander, Korg EX800, Roland MKS-30) he is in business.

There are six monophonic channels each with 1533 steps, and every channel can be assigned its own MIDI track so you could run six different synths. Composition is in the form of an unfolding chart — you type the channel number, the event number (1st note in the sequence, 2nd note etc), the note (E5 or C4, for example), its length (semi-quaver, quaver etc) and its gate time (whether it's played legato, staccato and so on).

And you carry on until the music's completed. You could write all of channel one first, then onto channel two, or write them simultaneously — channel one, 1st note, blah, blah, blah; channel two, 1st note, blah, blah, blah; channel three, 1st note... and ever onwards.

If you want to change sounds at any point, or feed in velocity data, you need to create a new event. Say at step 15 you want the next four notes to be on strings, and be louder. You'd insert a new instruction at 15 (whereupon all the pitch, length info for that step shuffles down onto 16, 16 goes to 17, you get the picture?). The new instruction would say what sound you wanted. For velocity (a value between 1 and 127) you'd write a new line at 16 and the shuffle happens again. To end that operation you'd get into the list at 21 and 22 to supply fresh sound and velocity info, or return it to the previous values. Doesn't it sound like a lot of hard work?

Fortunately Siel have included several invaluable time saving functions. "Copy" takes any number of steps (say 10 to 24) and, as the name rather cleverly implies, copies them in anywhere else (say 41 to 55). "Transfer" takes those notes and copies them into a new channel. "Transpose" shifts the whole block in pitch. So construction of a short 12 bar, for instance, would be a matter of typing perhaps 20 instructions rather than 200.

The composer has various default values so if you don't enter anything it will assume a note length of 24 (a quaver), gate time of 12 and velocity info of 64. Remember that for the 'average' note, the gate time should be half that of the length (12 for 24, 24 for a 48, etc), increasing it will produce a legato slur, decreasing it will go staccato.

You can play any one channel, or all six together, but by cunning fiddling — setting channels 3, 4 and 6 to an unconnected MIDI line, for example — you could play combinations.

You want to see what notes there are in a chord? Type L.120 which will then display the info for ail six channels at step 120. Again there are the refrain looping facilities plus a real time clock to show you how long you've been sequencing for.

Personally, the idea of seeing one of my songs as a never ending list of numbers doesn't over excite me. But the Siel has undeniably useful facilities and functions, and there is a certain fascination to being able to perfect a piece of music to the tiniest detail. At £34 for the cassette and £39 for the disc, it's also very reasonably priced.

And last, the real time, 16-track recorder. Several software companies are having a crack at this idea and so far they've attempted to mimic a real studio as closely as possible. Each channel is fully polyphonic, can operate a different synthesiser, and even bounce down and overdub so the notes on say, tracks 1, 2 and 3 can be copied together on track 4.

This is not how Siel have done it. Their system is more like 16 separate polyphonic sequencers that can be played in any combination, but not remixed. You record each track, to an audible metronome. The beat shifts to a higher pitch for a count of four, then you're in and playing. When you stop, that's it, the track is completed.

There's no going back at a later date to insert material or stretch the ending — it's straight on to the second track to add the bass line, extra chords, etc. Annoyingly you can't hear the original material as you record the new lines, a flaw that appears to be shared by most other real time software.

Once the tracks are filled, the Siel lets you dedicate them to a song. For Song 1, say, we'll have tracks 1 + 3 + 5 + 6, all playing together in sync. Siel visualise this being used by bands live who want to call up an entire arrangement of bass lines, backing etc, in one short instruction. They've also structured the program in this way to get the most economic use of the memory.

Nice touches are the disc directory so you can see what songs you've got (you can name them if you don't like numbers) and a program start instruction at the beginning of the sequence. This lets you set up a limit to the sound programs you can call so you're not asking a synth to go to patch 34 when its maximum is patch 32.

That's your lot. If you're looking for an overall philosophy from Siel, then it wouldn't be too wrong to say they want to get your music out of the machine as quickly as possible.

A fast turn around of ideas and sounds, no bad thing. One point that did emerge from the software trial is worth bearing in mind for Commodore users. Certain Commodores that came off the production line before November of last year may be fussy about taking real time information — one of the SXs we tried for the 16-track recorder didn't want to know. If this happens to you, take your machine back to the shop and ask for a 'Kernel 3 ROM' update. That will do the trick.

Siel software: £22-£64