Yamaha DX7IID
Two FM tone generators, sixteen-note polyphony, and the sound of a DX7 that finally learned to breathe.
Overview
The letter on the end is the whole story. On the DX7IID, the "D" stands for dual FM tone generators, and that single addition is what separates this machine from the original DX7 that made Yamaha's FM architecture a household sound. Where the first DX7 ran a single six-operator engine, the DX7IID carries two six-operator, 32-algorithm FM tone generators — the same dual architecture found in the company's flagship DX1 and DX5 keyboards. For players who spent years coaxing splits and layers out of a single-engine DX7, that second generator changes everything about how the instrument sits in a rig.
The practical payoff shows up in how the keyboard can be configured. Each keyboard functions as a 16-note polyphonic synthesizer in single mode, or as two independent eight-note sections in split mode, or as two layered eight-note voices in dual mode. A bass in the left hand and a lead in the right is no longer a compromise; layering two eight-note patches for a fat, stacked texture is now native to the instrument rather than a workaround. Recording Engineer (March 1987, p.106) described the dual-FM design as allowing the keyboard to operate as a 16-note single-mode, two-section split, or two-voice layered polysynth — the flexibility that defined the second-generation DX7.
Voice memory doubled over the original, to 64 internal (though some documents state 54) and 64 external on RAM cartridge. The DX7IID uses the larger-capacity RAM cartridge introduced with the II series, though cartridges for the original DX7 will still work in the new units, and the ADP1 cartridge adapter lets a RAM1 or other DX7 cartridge plug into the enhanced model. That backward compatibility matters to anyone with a shelf of old voice carts — the library carries forward.
The II series also broadened what "voice" means. On the original DX7, only voice data was stored; performance data like pitch bend and portamento couldn't be saved per voice. The DX7IID's expanded Performance Memory stores all pedal, mod and pitch wheel, pitch bend, and other function data for each voice.
Then there's Random Pitch Shift, which slightly and randomly detunes the pitch of each note. The intent, as Yamaha described it, is to simulate the warm sound of several acoustic instruments playing the same note at slightly different pitches — a small feature that does a surprising amount to keep stacked FM voices from sounding sterile and identical.
Tuning got serious attention too. The DX7II series allows the tuning of each key to be programmed, and the Micro Tune memory carries 11 presets including Mean Tone, Werckmeister, and Pythagorean, plus two user-programmable memories. For players working in early music or non-equal temperaments, that's a capability the original DX7 simply didn't offer. The front panel is a 40-character, two-line backlit LCD paired with two alpha-numeric LEDs, and the back panel includes left and right outputs with panning to position voices according to key touch, LFO, key velocity, or which part of the keyboard is being played. There are inputs for a breath controller and headphones.
What the DX7IID is not, notably, is the floppy-disk model. The DX7IIFD adds a built-in 3½-inch one-megabyte floppy drive for storing synth data and MIDI data from sequencers, drum machines, and other synthesizers. The DX7IID omits the drive and relies on RAM cartridges for external storage — which is the trade-off buyers weighed at the counter. Period dealer advertising listed the DX7IID at $1,695 and the DX7IIFD at $1,875, so the disk drive carried a real premium.
Yamaha's own framing at the Winter NAMM unveiling, roughly three and a half years after the original DX7 appeared, was that the II series added functions DX7 owners had asked for, new creative features, and — in the company's words — simply sounded better, while remaining totally compatible with the DX7. The compatibility claim is the important one for collectors: the vast existing library of six-operator DX and TX voices carries over, and the new parameters build on top of it rather than replacing it.
For anyone repairing or buying today, the DX7IID is the connoisseur's choice among the II-series keyboards for players who don't need onboard disk storage. It delivers the dual-FM architecture, the doubled voice memory, the per-voice performance data, the microtuning, and the random pitch shift — the substance of the second-generation DX7 — in the version that asks you to manage your library on cartridges. Whether that's a virtue or a nuisance depends entirely on how much you trust your RAM carts.
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