ONCE DESCRIBED BY PETER VETESSE AS "A GLORIOUSLY FLAWED INSTRUMENT", THE CS80 REMAINS ONE OF THE MOST UNRELIABLE YET SOUGHT-AFTER ANALOGUE SYNTHS OF ALL TIME.

FROM ITS RELEASE in January 1978 (after only a two-year development period) the CS80 was a mythical beast. It was such a monster that you never quite knew whether what people told you about it was true. There was stuff about it weighing more than a tone-wheel Hammond, and more stuff about Yamaha having to redesign it with differing value components depending on how close to the centre of the machine the component was, so that massive differences in temperature could be catered for. First some facts.

Number one: my CS80 doesn't get especially hot, but it is monstrously heavy. If you can imagine trying to lift Demis Roussos you'll know the sort of proposition. It weighs precisely 100kg, according to the handbook - roundabout the same as the L100 Hammond Keith Emerson used to massacre years before. In context, that's equivalent to seven JX10s. Don Snow, ex-Squeeze, ex-Sinceros keyboard player, and such an aficionado of the CS80 that he provided the review in Keyfax (the keyboardsman's secondhand bible), recalls several occasions when he had to manhandle his CS80 up and down stairs on his own, to get to a recording session. The technique going down was to hold it upright, ease it to the edge of the step, and then let gravity take over. Going up was the reverse of that, with him supplying the motive power instead of gravity. (He also tells of the time that he tried to get the beast into the back of his Reliant Robin, but that's another story.)

It's pretty easy to see why the CS80 weighs so much. For a start, it's built into its own flightcase; second, although the keyboard isn't very long - the 61 notes that has become the usual synth standard - it's very solid, with a well-engineered weighted action that's getting on for half-a-metre from front to back. Third, everything else about its construction is also ultra-solid. Fourth, if you ever manage to look inside, you'll see that it's packed tight with by far the most elaborate and dense analogue electronics ever seen in a synth. What this adds up to is an instrument which is great if you can keep it one place, but a roadie's nightmare (literally, in one case) if you want to take it anywhere.

The CS80's internal construction is really one of the most crucial elements in the story. There's so much more crammed into it than even its near contemporaries, like the Prophet 5 or the OBX (let alone a modern synth), that it looks as if it comes from a different era. And that was both its beauty and its downfall.

Back to the facts. In modern terminology the CS80 is an eight-voice machine, with two VCOs per voice, but it's really two separate eight-voice synthesisers operated by the same keyboard. Each synthesiser, or channel, has a really comprehensive range of controls. You have a choice of sawtooth and/or square waves, with sliders for adding sine wave or white noise. The square wave has three PWM sliders, to control the speed, the intensity and ratio of the modulating pulse.

The resultant wave combination can then be modified with a comprehensive filtering arrangement. High and low-pass filters are available, both with resonance controls. You've then got the usual ADSR controls, plus an extra attack level control. (Generally, Yamaha do a good job with making the CS80 intuitively easy to get to grips with, but their terminology here - Attack Level and Initial Level - is a mess.) The VCA is controlled by seven sliders, governing the amount of signal fed from the sine wave and/or VCF, the ADSR, and the overall level.

The CS80 doesn't have a proper split facility, but you can layer the two sounds and determine how the touch sensitivity (both velocity and aftertouch) is going to affect the VCAs and VCFs for each of them - velocity crossfading, in effect. The aftertouch, by the way, is polyphonic - like the Prophet t8 - so that pressure on one note affects only that note, not any others you're playing at the time. It goes a long way to making the synthesiser potentially as full of nuance and expression as a guitar.

The keyboard's versatility doesn't end there, either. You've got four levers to control how brightness and volume change across the five octaves. The other main performance control is a 510mm long pitch ribbon above the keyboard - which takes some getting used to after pitch wheels, but has a lot to be said for it, particularly as there's no detent - you just slide from wherever your finger first hits the ribbon. There's no modulation wheel - Yamaha obviously reckoned that with polyphonic aftertouch provided, you've got no need for one. Fair enough. (The pressure needed for aftertouch, incidentally, was described by Rod Argent as like doing weight-training; but it's no worse than a JX10.)

Other controls that come easily to hand include sliders for setting up overall brightness and resonance and controlling the mix between the two sounds; for setting portamento and sustain times, and for setting each channel's coarse tuning (in octaves or fifths) as well as detuning channel two. There's also a chorus/tremolo unit with variable speed and depth; and switches for portamento or glissando, and for making the supplied foot-pedal a volume control or a combined volume and filter pedal.

You can also decide whether the footswitch (supplied) should switch between portamento and glissando, or should act as a sustain pedal. The more you look at this instrument, the more clear it becomes that it was designed to be the ultimate performance instrument. More's the pity, then, that its sheer bulk and its awful reliability record, meant that so few were ever actually produced.

I sometimes wonder if all CS80's are as bad as each other when it comes to reliability. Perhaps somewhere there's a charmed example that sits in state in someone's studio and never goes out of tune, loses its presets, gets dirty keyboard contacts or goes ape on its keyboard sensitivity. If you find one like that - not one that's just been painstakingly serviced, but one that just doesn't ever seem to need servicing - then it's worth a fair bit of money.

It's more likely that you'll see CS80s advertised as "not totally working", with a "tuning problem" or needing "attention". If you've got the space and cash available, should you be tempted? I'd say yes - as long as you don't want it as your main synthesiser, or indeed as an instrument that you can rely on. But if you want a source of staggering off-the-wall stereo sounds, you've got to give it a go. Let's face it, with so many people having access to quality cheap technology it's the old stuff that's going to make your music sound different. Old stuff obviously includes instruments like guitar and sax - and voice - but it also includes more unusual synthesisers because they'll help give you individuality in an age of mass production, remember: you can solve problems of unreliability with a sampler.

You might still be wondering what makes the CS80 so special. OK, it's old-style analogue throughout where more recent "analogue" synths are either digital/analogue hybrids or use a master oscillator, so that all voices are phase-locked and lack those minor phase and pitch discrepancies that make sounds special. But that still leaves it serious competition: the Prophet 5, the Oberheims up to the OB8, the Memorymoog. What sets it apart from them?

Well there's the quality of the panel hardware and keyboard, plus the versatility of the performance options available from the keyboard's touch sensitivity. (None of the above list of classics even has velocity sensitivity.)

The quality of most of the CS80's preset sounds (when they're working) is definitely up there with the best analogue synthesisers ever produced, and while you are stuck with them for ever - no ROM changing or even cassette access - they're fair sounds to be stuck with. It's fascinating talking to different people about their favourite of the 22 available (from chunky illuminated buttons at the centre of the machine). Everyone is enthusiastic or even fanatical about several of the presets, but no two people have the same preference. All the presets have their merits, even if, for example, 'Guitar' doesn't have much in common with anything with a neck and six strings.

You do have a certain amount of programmability, with the potential to set up two sounds on the synth's controls, and a further four on miniature sliders that lurk under the block diagram on the top left of the machine. The sliders are small, and it's not easy to get that precise position that makes the sound how you want, but like all the hardware on the machine, they are such good quality that anything is actually possible.

Six programmable sounds to work with doesn't seem much, but it seemed pretty good in early 1978 against the non-programmable monosynths and the Polymoog (one memory, I believe). It seemed good until the Prophet's 40 memories (which were a good deal less reliable than the CS80's) appeared.

Even with such meagre memory, the beauty of the CS80 is that there are so many ways to articulate its voices. I've mentioned touch sensitivity and the chorus (analogue - warm and instantaneous in the way outboard chorus isn't), but maybe the best thing of all is the ring modulator section. It is this that helps give the CS much of its "organic" character.

The Prophet 5 scored with its poly-mod option, but the CS80's ring mod is a cut above in its ease of use and variety of sounds. You have five more dedicated levers to play with, and they produce a range of effects that are easily as good as the Prophet's, but a whole lot simpler to control. One sets the amount of modulation - and seems to change the wave-form as well; one sets the oscillator speed - from about 0.5Hz up to a few hundred (that's a guess, because the manual is laughably unhelpful). What that means is that as well as the really off-the-wall ring-mod associated with putting two pitched sounds together, you've got a wide range of LFO-type ring modulation that's actually usable in melodic contexts.

Perhaps the most exciting bit comes from a combination of the other three levers: Depth controls the extent of an automatic sweep of the ring mod oscillator, and Attack and 'Decay' control how long this sweep takes to get to and from maximum. In practice it's easy to use, and the results are stunning. It's possible to set the same effect up on any patchable synthesiser system, from a Roland 100M to a Matrix 12, but how often would you do it? On the CS80 it's there by your left hand - so you use it.

Someone else who loved the CS80 is Vangelis - come to think of it, his version is probably still in good order. In December '84 (after almost everyone else had "gone digital"), the Big V admitted to Dan Goldstein (in this very mag) that the CS80 was the best analogue synthesiser ever produced. Presumably, with the arrival of the Prophet t8/Synclavier, and master keyboards of real quality like the KX88 and MKB1000, he will have had to revise that judgement by now; but it's strong praise by anyone's standards.

The list of admirers of this instrument is long, and although the problems of portability and reliability mean that no-one in their right mind would now take a CS80 on tour, there are still a great number of people who look back on it as one of the great synths. Users included Brian and Roger Eno, Herbie Hancock, Andy Mackay, Kate Bush, Rick Wakeman, Klaus Schulze, Peter Vetesse, and the BBC Radiophonic Workshop.

Yamaha originally pitched the CS80 around about the £5000 mark, and it didn't get discounted that much because it was the leader of the day and rich musicians and record companies were willing to pay up. In real terms (as they say on party political broadcasts) that must be equivalent to around 12 grand today.

It's tempting to try to get hold of a CS80 that's less than perfect, and therefore cheap, and restore it. But be warned: inside there are 35 circuit boards all packed with components, and all hardwired. Just to pull one circuit board out involves 30 or 40 unsoldered connections. If you were to go through just those boards at the back one by one, you'd need to unsolder and resolder well over 1200 joints!

The situation is made worse by the fact that Yamaha designed lots of custom LSI chips for the CS80 - two digital for the keyboard, and eight analogue for synthesiser control. You can get hold of some nowadays (by special order from Japan) but not all. Which makes it a bit tricky if the one you need doesn't exist any more. All you can hope to do is get hold of another (dead) CS80 and cannibalise it, hoping that the same bit hasn't gone down on that one as well.

Should you decide to take on such a task and need a little help, Yamaha say that although they don't normally service CS80's, they could do one in an emergency. They also say that most parts are still available from Japan. Their labour costs are about £20 per hour. If that sounds too steep, or you're not claiming "emergency" status, London's Synthesiser Service Centre are quite confident that they can deal with any problem that comes up - in most cases without having to order special parts. Labour charges this time come in at £32.50 per hour. (See contacts at the end of this article.)

But despite all the problems, people don't seem likely to give up on the CS80. One defective CS80 advertised for sale recently was snapped up by people who were prepared to come over from Sweden, transport it back there, and then get out the soldering iron and scope. It looks as if analogue synth technology is going to make it into the 21st century.

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