This synth originally belonged to my Dad and Uncle who used it to create some really strange relaxation/meditation music called Stress Break. Their idea was to market it along with this crazy waterbed in a cone of silence stress relief dome-thingy that a guy they knew designed. The package never made it into the Sharper Image and busy 80s stock brokers and hedge fund managers continued to turn to Alcohol and Qualudes to decompress after a long day defrauding hard working American laborers. But I grew up on the sounds of this synthesizer (as well as stereo field recordings of crickets and lofi Drumulator kicks EQed to sound like a heartbeat), so I justy love the DX7.
This synth is a baffling monster at first. It is the biggest, baddest FM synth on the planet. FM stands for Frequency Modulation. The digitally controlled oscillators are called operators and they are used is specific algorithms to modulate eachother and mix together in certain ways (think super-omega ring modulators) based on a series of envelope settings that effect amplitude and pitch and therefore modulation amount andfrequency. This brave new world of synthesis coupled with the DX7 mk 1's impossible pushbutton interface made the classic FM synths of the mid 80s preset boxes for most musicians (though what a great set of presets, you all know that hard and bright DX7 electric piano simulation that was used by artists as diverse as Aaron Neville and Pearl Jam). That said, for serious nerds like me, deciphering FM synthesis and creating strange new patches was a holy mission when these synths fell out of favor during the grunge era and all-analog Acid House boom that followed.
The DX7-IIFD addresses some of the problems of the DX7 for gigging musicians who just use presets. They added a cartridge memory port so you could buy new preset cartridges programmed by the MIT-elves at Yamaha (they look very Atari) and load them in for instant gratification. They added a good LCD display and improved the push buttons so it might just be possible for a rocket scientist to program a patch using the actual user interface. They also put 2 DX7 engines under the hood and improved and expanded the keyboard allowing you to split the keyboard between 2 patches or to layer patches. The action felt a lot better too so the MIDI functionality got a lot better when it came to aftertouch and velocity, which is awesome on a synth with so many envelope parameters for each of its 6 operators (and did I mention all these envelopes can be made to effect and interact with eachother in wild and unimaginable ways?).
Even after wrapping my pointy head around FM synthesis as a concept and the complex architecture of the DX7-II I didn't unleash its full potential until Windows 95 and the internet exploded and nerds of an even more terrifying bent than me started creating mouse friendly graphical editors that could help you program the Yamaha FM synths... and best of all, they were released as freeware. Doom anyone? This was my Doom! Achievement unlocked.
In my opinion the DX7-IIFD is the best of all the Yamaha FM synths. It has more voices, more operators, more functionality as a sound design tool, performance instrument AND MIDI module and is just totally inspiring in every way. But don't got screwing with one of these f you don't have a day to waste learning the architecture and another few hours the next morning to get absorbed in the awesomeness you can create when you stop trying to emulate natural sounds and start generating tones no one has heard before because they never could exist in nature.
I dock this synth 1 star for being so powerful, complex and alien in conception and implementation that only the most determined dweebs can tame her. I don't think Yamaha could have made an on-board user interface that would be intelligible and streamlined with the technology of the day, but it doesn't change the fact that this synth is not for the faint of heart and can only be truly appreciated when slaved to your computer with 3rd party software.