[sdiy] Synergy FM [was: Re: DX7 hacking?]

[Veronica Merryfield]

According to Hal, the inventor of the Synergy, the FM origin of the DX and the Synergy are from the same place but Yamaha got in first with the patent. If anything, the Synergy's oscillator to oscillator routing flexibility makes it a much more powerful FM machine that the DXs for the time. But, DKS could not promote this when the Synergy came to market.

Each oscillator has as it's input a pitch value from the keyboard, an envelope and an input from another output's accumulator. Each oscillator also has an amplitude envelope and the output accumulator although several oscillators can output to one accumulator.

The routing of outputs to inputs is completely flexible. The two oscillator envelopes are tied to the oscillator. Frequency offsets are controlled through the pitch envelope.

All the DX algorithms can be done on the Synergy and I am told many of them were tried, mostly with success. The mostly part comes from the phase changing that happens in the Synergy to achieve amplitude control.

The heart of the Synergy is a dedicated ALU, implemented in TTL logic and controlled from software. By controlling the phase lookup a then expensive multiplier was avoided.

Many of the voices in the library do use some form of FM although a lot can be done with the envelope control. Many of Wendy Carlos patches that one might associate with FM use 3 of 4 oscillators and some clever use of the envelopes and avoid FM. Many of the patches with some form of noise, use over modulated FM.

I am still working away on my software version of the Synergy. One of the switchable enhancements I'm adding is to use a multiplier for amplitude control instead of the phase control, but I have implemented the phase control method. Of course, this implementatio can have many more oscillators :)

On 2012-07-01, at 2:36 PM, Lanterman, Aaron wrote:

> On Jun 30, 2012, at 3:27 PM, Barry Klein wrote:
> 
>> I was more wondering about the engine hacking. 
> 
> As an aside, the Digital Keyboards Synergy is actually a fairly powerful FM synthesizer. I guess that to avoid legal issues with Yamaha, they downplayed this (calling it "phase modulation" instead of "frequency modulation" -- but in many cases they're equivalent, and the DX series is really a PM implementation of the FM idea anyway), so a lot of folks don't know about it (and of course DX series synths outsold the Synergy by a factor of zillions-to-one or thereabouts.)
> 
> A Synergy voice has these little flags that you can set for each oscillator that determines whether it gets added to an accumulator (the "additive" aspect) or modulates the next oscillator. By twiddling these I suspect you could implement most of the DX algorithms, except for the ones with feedback (I can't recall or now if there's a way to implement feedback on the Synergy -- there might be on that I'm forgetting). It's been a while since I looked at it, though.
> 
> The Synergy is limited to 32 oscillators, so doing something like 6-op FM would drop you down to 5 voice polyphony (etc. etc.), but that's pretty good, actually.
> 
> Envelope scaling of oscillators on the Synergy is performed using a phasor-addition trick, so the phase relationships between the oscillators are always sliding around. This probably has an effect on the character of its FM relative to the Yamaha synths. 
> 
> I'm not sure how many of the Synergy library voices exploit this FM capability. A quick tour through the presets shows that at least a few do -- there are some with dense spectra that are (a) characteristic of FM-type sounds and (b) thins that you couldn't pull off additively with so oscillators. Some of the FM-ish tones, though, like xylophones or bells, that would be done with FM on a Yamaha, are probably just straight up additive on the Synergy (facilitated by really flexible frequency envelopes.)
> 
> Once you add the Synergy's pretty sophisticated envelopes, you have a really interesting machine that could give the DX series a run for its money -- that is, if Yamaha hadn't been able to get the price point as low as they did! If Digital Keyboards had access to ASIC design and fabrication facilities, history might have been different.
> 
> - Aaron
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