The Yamaha CS80 was the world's first truly polyphonic, 'commercially available' analogue synthesiser. ARP had already released their Omni polysynth. However, this used organ technology to provide the polyphony and all voices shared a common filter and envelope so it wasn't truly polyphonic in the strict sense of the word. The CS80 changed all this.

Released in 1977, the CS80 pre-dated the Prophet 5 by a year and the Oberheim OB-X by several years offering 8-voice polyphony with a 61-note weighted keyboard, polyphonic aftertouch and other performance controls. It was actually an off-shoot of Yamaha's prohibitively expensive ($60,000) flagship GX1 but even at a 'mere' $7,000, the CS80 was still beyond the reach of most people.

In itself, each voice was unremarkable.... a single VCO into a LPF into an HPF and into the final VCA with ADSR envelopes and LFOs for vibrato, filter sweeps and PWM except....

There were two of these per voice.

That's right... rather than using the 'standard' two-oscillators into a lowpass filter into VCA architecture that was common on most monosynths at the time (and which was to be adopted as the standard voice architecture by polysynths in later years), the CS80 had two totally separate synths on each of its eight voices so that, in effect, you were playing 2 x 8-voice synths from the keyboard. These could be set to produce different sounds making it possible to layer sounds effortlessly. Alternatively, both synths could be set to produce the same sound for big detuned textures.

The oscillator produced the standard sawtooth and square waveforms (simultaneously) but unusually, it also produced a sine wave which could be mixed in at the final VCA to add weight to the sound. PWM was possible and each oscillator had its own separate LFO for the purpose. There was also a noise generator with its own level silder.

The filters were resonant lowpass and highpass (12dB/Octave) which could be used independently or together as a bandpass filter. The filters have their own dedicated envelope but this was not the conventional ADSR type. Instead, it was ADR with curious 'INITIAL LEVEL' and 'ATTACK LEVEL' controls that not only set the start level of the envelope but could also be used to set sustain level... mmm... very confusing! The VCA was simpler having level controls for the filter output and the oscillator sinewave and a normal ADSR envelope. Each synth had controls to set their response to velocity and aftertouch.

What made the CS80 totally unique, however, was its performance controls which arguably remain unsurpassed even today!

The weighted keyboard's velocity could control amplitude, filter cutoff and a special pitch envelope whilst the keyboard's totally polyphonic aftertouch could control amplitude, filter cutoff, the pulse width LFO and the main LFO's speed and depth. Polyphonic aftertouch is something that has to be used to be believed. Basically, the aftertouch is available independently for each voice so you can hold down a chord and swell just one note in by pressing harder on one key (unlike conventional aftertouch where doing the same would affect all voices equally). One of the CS80's most famous users, Vangelis, used this to great effect in his music and you can hear it all over the sound track he wrote for the film Blade Runner and is a trademark sound in much of his music.

Furthermore, just above the keyboard were easily accessible master controls for brightness, resonance and tuning plus controls that governed velocity and aftertouch sensitivity. There was also a master LFO that offered a wide range of waveforms over a very wide frequency range. These affected both synth layers equally. There were also controls to set the octave for each layer plus a balance control to set the levels between the two synth layers and a separate control to detune the two synth layers. There were also controls to set the tonal balance across the keyboard range (BRILLIANCE) and also balance levels across the top and bottom of the keyboard.

There was also a ring modulator but instead of ring modulating the two synth sections as you might expect, it had its own modulating oscillator with an envelope that controlled that oscillator's pitch - thus the whole synth was processed through this unusual ring modulator for everything from subtle tremolo to out-and-out filthy clangs!

Unique to the CS80 was also its ribbon controller. Located just above the keyboard, this could be used for pitch bend sweeps of outrageous proportions. Unlike other ribbon controllers that have a fixed 'centre point', the CS80's uses the position you place your finger on first as the centre point - by pressing the top of the controller and sliding down, you have a pitch bend range that goes sub-sonic! Such was the length and range of the ribbon controller, it could almost be used as an Ondes Martenot or Theremin and with practice, you could play tunes on it!

To the left of the keyboard was a panel that housed further controls for sustain plus tremolo and chorus effects. It also housed controls for portamento and glissando (quantized portamento that moves in steps - unique at the time and still uncommon today).

The CS80 was also the first synth to provide memories... after a fashion. Just above the ribbon controller were two rows of 14 brightly coloured buttons that selected 11 factory presets for each synth layer thus making it very quick and easy to layer different sounds. However, you could also store your own sounds.

Top left on the upper panel was a lid. Underneath this were four banks of miniature sliders that were a duplication of the main panel controls. You set these controls for the sound you wanted to 'store' and these could then be recalled using the four white memory buttons (2 user memories for each layer) at the far right of the presets bank. It was primitive but it worked! Two further memory buttons effectively provided two extra user memories - the settings on the main panel!

All these combined made the CS80 a truly unique synthesiser not only of its time but even today, its performance capabilities have yet to be surpassed.

But there was a downside to the CS80.

Firstly, it was big (47.5 X 12 X 27 inches) and heavy (220lbs). Also, each voice was a completely separate synthesiser on its own circuit board and so tuning and calibration could be a nightmare. There was also enough wiring inside to span the equator several times! The calibration controls were on 'trimmer' pots on the circuit boards and if the thing was being transported around, these could slip requiring a complete overhaul before the gig!

In the studio, however, the CS80 is quite well behaved and the fact that each voice is a synth in itself is actually a contributing factor to the depth and richness of the sound as no two notes ever sound quite the same, however well calibrated the boards may be.

There are no less than 21 samples taken every minor third (C, D#, F# and A for every octave) taken from the donor's own own original CS80 and because each sample uses a different voice card, each one is subtly different. You don't hear it when each sample is played in isolation but played in chords, the sound is supremely rich.

Samples kindly donated by regular Hollow Sun donor, Marcel Donné