DX7 programming (Was [sdiy] Steel drum synth)

Batz Goodfortune batzman at all-electric.com
Sun Jun 23 14:38:42 CEST 2002


Y-ellow all.
         Of course it has to be said that the Chowning work is the original 
thing and if all you want to do is patch a DX7 then it might be a bit heavy 
going.

Whilst I don't have the inclination or time to explain a DX here, I don't 
understand why people have so much trouble with these things. Ok so I admit 
granular synthesis breaks my brain somewhat but FM shouldn't be that hard 
for a DIY-er to understand. And I don't know why people constantly say it's 
hard in that the parameters have no relationship to the end result.

Even if you don't understand any of the more interesting details, the rule 
of thumb is this. Any modulator is going to introduce higher frequency 
artifacts even if the modulator (the operator on top) is at the same 
frequency as the carrier. (The operator on the bottom)

As someone on AH rightly pointed out many many years ago, it really should 
be called PM synthesis not FM in the case of a DX7. Because the carrier's 
fundamental is always locked to the keyboard. It's phase is modulated by 
the operators above it which means it doesn't change it's frequency as 
such, it changes it's shape or phase transient. Thus it remains musically 
useful.

However, Just think of FM radio. The Amplitude of the signal is constant 
and the frequency is set at a centre point. This frequency is the nominal 
frequency and when a signal is applied it deviates up and down in frequency 
depending on the modulation signal. IE: music.

The advantage of FM synthesis over say, recombinant harmonic synthsis AKA 
additive synthesis, is that you can far more harmonics with far fewer 
operators. But this very fact means that it takes far more subtlety to 
program so the best advise anyone could give with a DX7, and the advice 
we've been giving for years, is to never try and start from scratch. The 
best way to get what you want out of Yamaha's FM synthesis system is to 
find a patch you like and then tweak it till it does what you want. It 
doesn't mean you don't still have to understand the basic principals of FM 
(according to Yamaha) but you'll arrive at the same point a hell of a lot 
quicker.

Most of the books I've flipped through on FM over the years have dispensed 
not very useful advice IMHO. Most don't even mention the above rules of 
thumb but tend to focus on how magic the algorithms are. There use to be a 
really good DX7 mailing list run by Dave Benson. I don't know if it's still 
out there but he also had a very extensive resource site for the DX. 
Including scanned manuals and programming information. Not to mention a 
g'zillion patches ready to abuse.

You can find the page here and contact Dave for List subs. 
ftp://byrd.math.uga.edu/pub/html/dx7.html Tell 'im Batz sent you. :)

Be absolutely Icebox.

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