Looking in detail at the GX1's voice and performance structure only heightens the impression that this was, and is, a remarkable instrument. Mind you, you can't do this by looking at the instrument itself, because you can only create a sound using the optional programmer and "Tone Module Setting Box", which may be even rarer than the GX1 itself.
On the GX1's top lid, above all the manuals and controls, are four panels which flip up to reveal the huge circuit boards that host the Tone Cartridges. These cartridges, which are about the size of a matchbox, each contain 26 tiny potentiometers that determine the values of the circuits creating a single GX1 Tone. In other words, each cartridge is, in essence, the top panel of a conventional analogue polysynth.
There are two types of cartridges: Fixed Tone Modules, and Programmable Tone Modules. As you might expect, you cannot adjust the Fixed Modules; these provide the 'factory' Tones supplied by Yamaha (see box). The Programmable Modules, by contrast, allow you to access the potentiometers that define the Tone. Unfortunately, you can't reach these when the cartridge is inside the GX1, so you have to remove it and connect the cable from the programmer in its place. Once attached, the programmer then duplicates that cartridge's functions, thus fooling the GX1 into thinking that the cartridge is present. Now, of course, you can adjust that Tone (but only that one) just as you would if the GX1 was a conventional synth with a control panel.
The Setting Box has two switches, a large selector with positions 1 to 26, and three lights called 'To Right', 'To Left', and 'OK'. Once you've programmed a Tone you want to store, you plug the Tone Cartridge you wish to program into one side of the Setting Box, and the programmer itself -- being careful not to knock any of its knobs or sliders -- into the other. Having done so, you set the large knob on the Setting Box to '1' and check whether the To Left or To Right lamp is lit. Then, locating micro-screw '1' on the cartridge, you turn it in the required direction until the 'OK' lamp lights. Now you rotate the selector to '2', locate screw 2, and repeat the operation. You do this until you have set all 26 screws correctly, at which point the resistances of the 26 tiny potentiometers in the cartridge echo those of the much larger ones in the programmer.
You think I'm joking, don't you? Well, I'm not. Next, you remove the cartridge from the Setting Box and insert it into the desired slot in the GX1 itself. Simple! Actually, it's not just simple, it's brilliant. Three years before the Z80 microprocessor allowed Sequential Circuits to incorporate 40 patch memories into the Prophet 5, the GX1 offered 70 Tone memories with none of the parameter quantisation of microprocessor-contolled synths.
