Yamaha GX1

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Yamaha GX-1
Manufactured byYamaha
Dates1973 - 1977
Technical specifications
Polyphony2 x polyphonic sections
with 8 note dual-osc polyphony

Solo section single-osc monophonic

Pedal section with triple-osc monophonic
OscillatorSolo section - 1

Upper and Lower poly sections - 2 per voice

Pedal section - 3
Synthesis typeAnalog Subtractive
Filtervoltage controlled 2-pole low-pass and high-pass filters per oscillator
static band-pass and high-pass filters on sawtooth and square waves only
Attenuator2 envelope generators
Effects2 x spring reverb
Keyboard1 x 61-key, horizontal aftertouch
1 x 61 key
37-key, velocity, vertical and horizontal aftertouch
25 pedals
External controlNone

The Yamaha GX-1, along with its predecessor, the Electone GX-707, is an analog polyphonic synthesizer developed by Yamaha as a test bed for later consumer synths. The GX-1 has four synthesizer "ranks" or manuals, called Solo, Upper, Lower and Pedal, plus an analog rhythm machine.
The Solo rank features a 3-octave, 37-key keyboard with full-width, but shorter than normal keys. Directly above the Solo keyboard runs the Portamento keyboard - a ribbon controller which can be used to play continuously variable pitches roughly corresponding to the Solo keyboard note below. The Portamento keyboard over-rides the solo keyboard if used simultaneously. The Solo rank has only a single oscillator, but has a dedicated LFO, pitch envelope generator and ring-modulator.
The Upper and Lower ranks each have a full-sized 5-octave, 61-note keyboard. They are both 8-voice polyphonic, with two oscillators per voice. Each poly rank has a dedicated LFO, and there is a common "random" modulation generator. The Upper rank also has horizontal aftertouch which can be assigned to pitch, volume or filter, and a polyphonic glide function.
The Pedal rank has a 25-note pedalboard. It is monophonic, with three oscillators but no LFO. Performance controls include a "swell" pedal with footswitch, and a spring-loaded knee controller.

All four ranks use a common voice-card design (called a tone generator in Yamaha parlance) to produce their sounds. Each voice card features a voltage controlled oscillator with multiple waveforms, 2-pole high-pass and low-pass voltage controlled filters, and two envelope generators for filter modulation and VCA control. There is also a variable band-pass filtered sawtooth wave, and high-pass filtered square wave on each card. There are a total of 36 voice cards in a GX-1, containing 36 oscillators, 72 envelope generators, and 144 filters. Due to the extensive use of epoxy-potted sub-modules, a complete set of GX-1 voice cards alone weighs more than a Polymoog.

Preset sounds are stored on "tone modules" - small cartridges which each contain 26 fixed value resistor-dividers. These produce voltages which drive the voice cards, each resistor controlling one parameter of the sound. The tone modules are installed in compartments on the top panel of the synth. An optional "tone board" programmer could be inserted in place of a tone module, providing a full set of knobs, switches and sliders to control the parameters of a tone manually. Tones created this way could then be "programmed" onto a variable tone module using the Tone Module Setting Box. The Upper, Lower and Pedal ranks all have a dual-voice structure, where a different tone is assigned to each of the two voice cards per note. A set of hidden "wave motion" controls allows the second tones of the Upper and Lower ranks to be de-tuned. In the Pedal rank, the second tone is doubled on two voice-cards, both of which have a separate de-tune control.

The GX-1 console weighs 300 kg. The pedalboard and stand add 87 kg, and each of its tube-powered speakers, four of which can be connected to the GX-1, weighs 141 kg (Which together, equals 528 kg, or 1,164 lb).

The GX-1 cost $60,000, and was premiered in the US in 1973 at the NAMM convention. The exact production number is unknown, but supposed to be less than 100, and at least 13 GX-1s are known to exist outside Japan. Presumably, the majority of GX-1s never left.

Some of the people to use it extensively were Keith Emerson, John Paul Jones of Led Zeppelin (who later sold his to Keith Emerson as a spare instrument), Stevie Wonder (who is said to have bought two, one of which is on display at Madame Tussaud's in Las Vegas), Benny Andersson of ABBA (This GX-1 is now located at Roth Händle studios in Stockholm), Hans Zimmer (who bought Keith Emerson's old GX-1) Rick van der Linden of Ekseption, and Richard D. James (Aphex Twin). Rick Wright of Pink Floyd allegedly owned one for a brief time, but it did not make an appearance on any recordings.

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