DX7 Harmonica

[martinvicanek]

Hi crowd,
I reverse-engineered the DX7 harmonica sound. Remember the eighties, Tina Turner, Chaka Khan? I think I got the basics right, however I had only this one sound sample to work with, not the real instrument. So if somebody wants to refine, go ahead!

[tulamide]

Sounds quite good. It can't be the original, which I can tell from the schematic. But maybe that would be an interesting community project? Recreating the DX7, rather than imitating it?

The heart of that synth are the operators. In Yamaha slang this means a group of oscillator, amplifier and envelope. Such an operator has inputs (for example to the osc, to the envelope, etc.) and one output. This output can either be routed to the DAC, in that case it is called a "carrier". Or it can be routed to any input, then it is called a "modulator". The DX7 had 6 operators that could be freely distributed as carriers or modulators (well, almost freely; it had 32 premade combinations, called an "algorithm", that you could select from).

The concept is still great, I think, especially with the unison mono mode, where all 16 note polyphony was used to create one 16 voice unison sound.

[martinvicanek]

I should have written more details about my approach. Yes, my device uses FM syntesis (or more precisely phase modulation synthesis), just like the DX7. The spectrum of the original sound sample (top) is a fingerprint of the algorithm (= configuration of modulators and carriers).

DX7 Harmonica Spectra.png (139.33 KiB) Viewed 38492 times

Take for instance the symmetric pattern at the 10th harmonic, which repeats itself al tower level at the 20th harmonic. That tells you that there is a modulator at ten times the fundamental frequency, and from the repeated image you can infer the modulation index to be around 0,07. Then you can analyze more details like the dominance of the second harmonic etc. and get more hints. The synthesized spectrum (bottom) is actually quite similar to the original. That's why I said I think I got the basics right.

Of course there is more to the sound than just the spectrum, like envelopes, LFOs, keyboard tracking etc. Those are the refinements I had in mind, if somebody wants to chime in.

[Spogg]

Hey Martin
This sounds very authentic.
I used to own a DX7 just after they came out and it was a great and surprising machine; such a huge leap forward from subtractive synthesis which was the norm back in the day. Since the method is so powerful I incorporate FM (actually Phase modulation or Phase distortion as Casio named it) into my own synths. I experimented with true FM Vs PM and I prefer PM. The results sound more musical to me for some reason.
It should indeed be possible and quite straightforward to re-create the DX7 inside Flowstone. It would need 6 identical modules containing, as you say, the requisite envelopes, key scaling etc. Then add a routing matrix to make preset algorithms. Or, for more flexibility maybe, use the patching system I've seen here.
With my own DX7 I found that some algorithms were far more useful than others. Generally I preferred the ones that had three or four outputs to the bus with only one modulator each. This tends towards my Quilcom Adder which has up to 16 outputs with an FM bus for all partial oscillators with per-partial level control. This is not the idea of the DX7 but it enables a vastly extended repertoire of sounds to enhance and modify the basic additive scheme. FM, even in small amounts, can really liven up the sounds.

You may find this link interesting:

http://asb2m10.github.io/dexed/

This guy has made a DX7 editor that also contains the synth itself. I tried it a while back and it's a damn fine emulation. I even got hold of the original cartridges as sysex data, loaded them in and suddenly I had my old synth back again. So, I can vouch for the accuracy of the sounds and if you want to sample and analyse the waves this plugin is probably the closest you will get to having an actual DX7.

Cheers

Spogg

[tulamide]

Martin,

maybe I wasn't using the right words, in which case I'm very sorry. What I meant was that there's only one amp/envelope for all oscillators instead of one per used oscillator, so that's what I meant when I said "it can't be the original". I didn't want to disparage your work, or something! On the contrary, I thought your example could be a wonderful basis for a complete modelled DX7 and that it would be great if many people would contribute to it.

Btw, I'm sure there are two details that most emulators don't take care of: The velocity range was 1-100 (instead of 127) and the digital technology was all so new (and expensive), that the resolution was only 12bit. So a velocity mapper and some kind of bit-reducer would add to the authenticity.

[tiffy]

Thanks for sharing Martin. It sounds real nice.

[martinvicanek]

Thanks for your feedback, guys.

tulamide, don't worry, no offense taken at all. You are right, the DX7 has many more parameters than my little schematic, I just wanted to explain why I thought that I had the essence right. Apologies if I sounded mad.

To emulate the whole instrument would be a huge project, though it would be cool to be able to load any of the legendary (or not so) sounds available out there for free.

Spogg, thanks for the link, definitely will check it out when I have time.

BTW I am looking for a way to synthesize a fretless bass sound and possibly an upright bass sound. It doesn't have to be a faithful imitation - it will never be - I'd be happy with capturing the typical characteristics of the respective sound. Schematics, patches, samples anyone?

[tulamide]

BTW I am looking for a way to synthesize a fretless bass sound and possibly an upright bass sound. It doesn't have to be a faithful imitation - it will never be - I'd be happy with capturing the typical characteristics of the respective sound. Schematics, patches, samples anyone?

Would any of these help you? From my sound library, played in a musical context with varying velocity, each 4 bar loop a different instrument. In order as they appear:
Upright 1
Upright 2
Upright 1 + harmonics
harmonics only
Fretless Jazz
Fretless Layered

mp3: https://db.tt/sVBtSK89

If you could use them, just tell me which one(s), and which notes and velocities

[Spogg]

What I meant was that there's only one amp/envelope for all oscillators instead of one per used oscillator

I checked this on the Yamaha site's manual for the DX7 and, as I thought and remembered, there is an envelope for each of the 6 operators. Each and every operator (osc) has 20 parameters. Some parameters have a rather coarse range too.
In fact, to build an accurate emulation, the info in the manual is invaluable.

Cheers

Spogg

[tulamide]

I checked this on the Yamaha site's manual for the DX7 and, as I thought and remembered, there is an envelope for each of the 6 operators.

Yep, that's what I said. (Remember, as described by me in my first post, "operator" is a fixed definition and means "a group consisting of an osc, an amp and an envelope")

In Martin's schematic instead there are a couple of oscs that all share one envelope.

Maybe I shouldn't post at all, it seems that either my English is so bad or people don't want to understand me - whatever it is, it is annoying for both sides.