January 19 saw the rather belated official release of a new synthesiser from Electronic Music Studios (London) Ltd, or as you probably know them, EMS; belated because of a fire which delayed the press extravaganza at their Oxfordshire country residence from before Christmas.

It was worth the wait, however. EMS are, of course, pioneers in the field of British synthesiser development: their famous VCS-3 was one of the first synths generally available. They also have a unique capacity for coming up with novel solutions to design problems, as evidenced by the matrix-panel patching system developed for the Synthi series, one of the earliest patching systems to do away with patch-cords without sacrificing flexibility. But EMS have always aimed at the experimental/educational music field: very often the idea of a keyboard, for example, appears to have been as an 'optional extra' rather than standard. And while this has encouraged many musicians to experiment with sounds rather than notes, it has no doubt affected sales, partially because of the notorious scale-setting exercise and also because the very flexibility of a unit like the VSC-3 limits its application on stage.

Yet EMS synthesisers have always represented significant steps forward in synthesiser design: apart from the VCS-3/Synthi-A series, and the monster Synthi-100 (each instrument fully customised right down to the name: the BBC Radiophonic Workshop's one, for example, being the 'Delaware' after the road which passes outside their BBC Maida Vale location), there's been the innovative AKS sequencer and its newer descendant, the Universal Sequencer, and the remarkable Computer Synthi. Even the Oxfordshire computer music studio itself is pretty well unique, although several EMS engineers have been filched by multi-million pound operations like IRCAM in Paris, leaving certain remarkable devices inoperable. But such is life (for more about the EMS studio itself, see our articles in the October and November 1978 issues).

With the new machine, the Polysynthi, however, EMS may well find themselves hitting the jackpot as far as commercial success is concerned. Because the new machine is not only fully polyphonic (ie you can play any or all notes at once, unlike certain other machines which offer a maximum number of 'voices' and notes that can be played simultaneously — often no more than four or eight — and which are better referred to as 'multiphonic'), it also has an integral keyboard (49 notes, C to C) and is aimed fairly and squarely at more-or-less 'instant' musical applications, ie the live gig and the normal recording session.

But unlike the majority of other polyphonic keyboards presently available, this machine doesn't rely on an array of presets: each sound is constructed from the basic building blocks of audio synthesis as and when required. At first sight this would appear to be cumbersome, but the colour-coded sections and controls are carefully designed to facilitate the quick and easy production of a wanted sound. The lack of presets is also no disadvantage: although there's always the tendency to go straight to page one of the 'Musician's Book Of Synthesiser Sounds' and use that for everything whether it's the right sound or not with a 'variable' machine like this, presets tend to discourage experimentation whereas a fully variable machine practically forces you to get to know the controls properly before you use it on gigs. I know one session muso, for instance, who disliked the Polymoog when it first came out, because after having run through the presets he couldn't think of anything else; he just hadn't spent the time needed to understand the machine and come to terms with its huge possibilities. The Polysynthi will probably suffer less from this hangup than many others, though, because of its good layout.

At first sight, the red, blue and yellow panels of the Polysynthi seem a little gaudy, but on thinking about it for a moment, I reckon it would be easy to see on a darkened stage, and is thus a good idea. The panel itself is divided into three major blocks: from left to right, two red 'Controls' panels, one blue 'Sources' panel, and two yellow 'Treatments' sections. Beneath these are the routing switches, which we'll come to later.

We'll start at the centre section, the Sources. At the top are two knobs, for noise and external input, and below these are the three waveform output level controls from the oscillator bank: pulse, square and triangular. The actual sound levels produced by all available sources can thus be mixed with a suitable combination of settings here. The oscillator bank output is derived from a single master crystal oscillator, divided down for each note. The use of a crystal generator in this way ensures maximum frequency stability despite changes of temperature, etc: it also ensures that the oscillator is in tune from switch-on. Likewise, the individual notes cannot drift in their relationship to another, contrary to the situation on some units which use completely separate oscillators. Beneath these (green-coded) knobs is a simple on-off switch for keyboard 'memory'. In the 'on' position, this holds the last note or chord played indefinitely; 'off', the note ceases when the keys are released, and this automatically sets the ADSR release (see later) to 'fast'. Beneath this switch is a master tuning control, and to the right of this, a rather stunning 'Range' knob. Stunning, because this control, calibrated in the common 'organ pipe' form, runs from 32ft (putting the lowest bottom note at a pretty-well sub-audible frequency) right up to 1ft (giving you a highest top note which must be round about 15kHz!). This switch, plus the 4-octave keyboard, gives you a nine-octave range, C to C: no lack of possibilities here. A final knob varies the control voltage level. Available sources also include white noise and external inputs.

On to the Controls. The left hand panel of this block offers an envelope follower with gain and threshold controls and a LED to indicate triggering: the gain control matches the unit to an input, and the threshold control sets a level, above which a trigger pulse is applied to ADSR 1. Beneath this are two identical LFOs, producing sine or variable-width pulse outputs in the range 12 seconds per cycle to 20Hz. A 'Rate' control sets the repetition frequency which may also be varied by the other LEO, the keyboard, or the envelope generators. The 'Pulse Width' control varies the mark-space ratio and these oscillators may be applied via the routing busses to the ADSR sections. And there's a level control on the end.

Next to the LFOs are the envelope generators, which are of the ADSR (Attack-Decay-Sustain-Release) type, each parameter being completely variable. Triggering is via the LFOs or the keyboard, and ADSR1 may also be driven from the envelope follower. A switch on each ADSR inverts the envelope waveform set up with the other controls. Beneath these switches are the 'Complete Attack' switches which are worth a little explaining. With a slow attack-rate, this facility enables you to determine whether you want the envelope to go on to the peak value when the keys are released, or straight into the 'release' section of the envelope. Both ADSRs appear on the routing switches, but they're also connected direct so that ADSR1 goes to the VCF and ADSR2 fires into the VCA, the signal amplitude being set by the 'Direct Control' knobs on the VCA and VCF.

The voltage-controlled amplifier and filter are in the first half of the yellow-coded Treatments sections, to the right of the Sources panel. The VCF is a 2- and 4-pole device, offering sharp filtering on the 4-pole setting (24dB per octave) and a broader roll-off of 12dB/octave on the 2-pole setting. Frequency is variable, as is the Q of the filter. The filter frequency may be controlled from keyboard, ADSRs or the low frequency oscillators. External frequency control is also possible with a foot-pedal. In addition (these specs seem endlessly remarkable!) ADSR1 can be used to sweep the filter frequency by an amount set by the 'Direct Control' twiddler.

VCF output is fed to the VCA, which has an adjustable initial gain. It is controllable in the same variety of ways as the filter, with a swell-pedal option.

Pleasantly surprising as a part of an instrument is the addition of an analogue delay line, which is driven from the VCA, with a mix control adjusting the balance between direct and processed signals at the output. Yet this is no ordinary ADL: like the rest of the synth, it too is voltage-controlled, offering chorus and repeat effects which may be used in the normal way, plus reverb via the feedback control (variable from zero to howlround) but with the additional possibility of varying the delay time with the ADSRs, LFOs or keyboard voltages, permitting a number of weird effects like repeats which rise or fall in pitch, and a quite respectable up or down arpeggio effect. Two switches select Chorus/Echo, and Echo long/short.

Even the keyboard has a lot to commend it. It has a very pleasant feel, positive yet smooth; it provides pitch information for the VCO bank plus two control voltages: one corresponds to the highest note played and the other is proportional to the pressure applied to the keyboard as a whole, which moves downwards when a note is pressed hard, offering control of dynamics. Both control voltages are distributed via the routing busses. To the left of the keyboard is a large pitchbend knob, with a smooth rotary action and spring-return to the zero position from either direction.

The routing busses, situated just above the keyboard, enable the various available control voltages to be switched through to any desired unit, via sturdy, positive three-position switches confirmed in action by red and green LEDs where appropriate, allowing selection between the two LFOs, ADSRs and keyboard voltages as sources for voltage control of every part of the audio signal generation and modification process. Yet the routing is simple, and easy to accomplish.

Having considered the impressive front, let's take a peek round the back of the instrument. On the rear left of the machine we find the standard jack sockets which handle external inputs, the three pedal controllers, and the output; the external input may be switched to Line or Mic levels. Also on the rear is the multiway socket which enables the Polysynthi to be connected to a rather remarkable polyphonic sequencer — no mods required — which is being developed for it.

The sequencer was only visible in prototype form when we saw it, but even that was pretty stunning. Based on the Z-80 microprocessor, the sequencer can handle up to ten minutes of polyphonic music (gulp!) plus things like harmonies, octave switchings, and other things you don't normally find. Then there are even more surprises. For example, editing and other operations like moving bits around, adding, subtracting and correcting are easy, and you can get the machine to play a recorded sequence once, any number of times without stopping, or continuously, and you can play further parts into the sequencer's memory as the sequence is being replayed. So you can run the sequence round and round and add more and more notes until all 49 are playing simultaneously (not that you'd ever want to go that far!). The prototype sequencer included a keypad for programming the Z-80 for these and other functions, but production models will select pre-programmed facilities simply.

Graham Hinton, the designer of the Polysynthi, has definitely put a lot of thought into this instrument, which not only offers excellent value for money (£800 for the synth and a projected £500 approx for the sequencer) but also promises to be yet another significant synthesiser development from the team at EMS, as it combines comprehensive control, flexibility and great versatility with remarkable simplicity which will no doubt make the instrument easy for musicians to come to terms with and use creatively. Most important of all, the sound is great, with a rich bass end and clear top, and no discernible distortions or other nasties.

If the Polysynthi fails to sell, it will not be because of the instrument itself. But this is EMS' first serious foray into the high-pressure commercial world, and — as top man Peter Zinovieff himself admitted — they have a lot to learn in terms of marketing in this area. The demonstration we attended, for example, was rather a shambles and something of an unhappy anticlimax to the excellent meal that preceded it. Although a fairly large — and interesting — group of people turned up, including such people as David Vorhaus from Kaleidophon and Eric Forder from Universal Edition, plus several other notables, journalists and not a few dealers, I wonder how much they got out of it all. Hopefully, however, with good promotion and so on the instrument will take off and do well for EMS, which is exactly what the instrument and its designers deserve.

For further details, contact Electronic Music Studios (London) Limited, c/o Peter Zinovieff, (Contact Details).