How do you fake the FM sound?

Started by MusicOverGear, October 02, 2014, 09:21:06 AM

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MusicOverGear

I recently made a Harmonica patch and wanted to see whether I could make it go from "real" harmonica to the DX7 harmonica sound that was in approximately 60% of all pop songs in the 1980's. I listened to each and thought maybe chorus/flange, and a flanger with speed set to zero actually did get some of the effect.

I'm wondering what's at work here and how can get results predictably. I've been reading about sound design but I haven't come across any discussion of faking FM sounds.

BTW Ring mod is an option on some sounds, but not on all. I don't have a Ring mod effect, just the Ring Mod calculation algorithm for combining the two oscillators in the GP-10.

NOTE this is not a GP-10 question - just synthesis in general. Also I'm interested in the theory more than "getting" the sound. I can get the sounds easily enough by schlepping a notebook computer, but I'm very interested in faking the FM sound. Seems like must be a mature art. There must have been a lot of people doing this in early-mid 1980's as people were still paying off their Phophets and Jupiters, hearing the DX7 sound burn over the whole earth LOL. I am planning to revisit the Designing Sound book and another resource on modulation effects, but I'm hoping somebody can get me started and point me toward a line of inquiry.

Thanks,
Michael

Elantric

#1
The old trick we used in the old days was use a real harmonica for the first bar or two, then use your "synth" harmonica.

Most folks will think the whole thing was done with a real harmonica.

And these are cheap

supernicd

I would think it would be tough.  None of the Roland guitar synths as far as I know have an FM algorithm.  The GR-55 has sampled FM sounds so you could fake it there as long as one of the samples happen to match up to the sound you want.

Ring modulation is actually based on and more akin to amplitude modulation than frequency modulation.  It has an entirely different effect on the sound.  Frequency modulation actually changes the timbre of the carrier wave by modulating it with the modulator wave.  It modifies the carrier's frequency (very fast) as opposed to it's amplitude (like AM or ring mod).  In real FM then, it's very common to modulate the modulator wave with an envelope, LFO, or even another oscillator to get some of the distinct FM types sounds.

You could probably fake some sounds FM sounds in subtractive synthesis by modulating the filter.  But in general a classic Moog subtractive synth has a different sound palette than a Yahama DX7.  You might be able to create similar patches on each but each will also be able to make sounds the other can't.

Anyway, my intent isn't to discourage you from trying.  It's a fascinating topic. :)  And even though ring mod is mathematically very different from FM, I'd think that'd be a good starting point to try to fake things.  If you're able to employ a ring mod in your patch, maybe modulating some of it's parameters with the internal wave pedal LFO might get some interesting faux FM results too...  I've not really tried it but it's a thought.
Strat w/ GK-3, Godin LGXT
VG-99, GR-55, GP-10
---------------------------------------------------------------

montyrivers

An intelligent ring mod and using delay effect feedback can get you pretty close.

Brent Flash

#4
Quote from: MusicOverGear on October 02, 2014, 09:21:06 AM
I recently made a Harmonica patch and wanted to see whether I could make it go from "real" harmonica to the DX7 harmonica sound that was in approximately 60% of all pop songs in the 1980's. I listened to each and thought maybe chorus/flange, and a flanger with speed set to zero actually did get some of the effect.

I'm wondering what's at work here and how can get results predictably. I've been reading about sound design but I haven't come across any discussion of faking FM sounds.

BTW Ring mod is an option on some sounds, but not on all. I don't have a Ring mod effect, just the Ring Mod calculation algorithm for combining the two oscillators in the GP-10.

NOTE this is not a GP-10 question - just synthesis in general. Also I'm interested in the theory more than "getting" the sound. I can get the sounds easily enough by schlepping a notebook computer, but I'm very interested in faking the FM sound. Seems like must be a mature art. There must have been a lot of people doing this in early-mid 1980's as people were still paying off their Phophets and Jupiters, hearing the DX7 sound burn over the whole earth LOL. I am planning to revisit the Designing Sound book and another resource on modulation effects, but I'm hoping somebody can get me started and point me toward a line of inquiry.

Thanks,
Michael
If you think an explanation of how FM synthesis works and how the DX7 used it will help, here is what I can remember.

The original DX7 had six operator algorithms (predetermined configurations called algorithms). An operator (Yamaha's name for it) was an oscillator that only generated a sine wave (like an organ tone) at a frequency of choice. Along with this you had envelops for frequency and amplitude available to shape the simple sine wave. The keyboard could also use envelopes using velocity to give dynamics, triggers, etc. If you had an algorithm of six on the ground level (or output level) you would get six sine wave tones of whatever pitch you selected, sort of like drawbars on an organ if you wished. This was the simplest way to create sounds.

Where the art came in was when you selected an algorithm that had stacked operators. When you stacked two or more operators these stacked operators would feed into the operator it was on top of and modulate (change) the sine wave into a more complex wave form depending on the frequency, amplitude, and envelope for frequency and amplitude applied to the modulating operator. You could also have the operator modulate itself to change the sine wave into another sound. If you had two operators stacked and the other four single on the output level you would get five tones, four of them sine waves and the fifth would be a modulated sine wave. If you had six stacked on top of each other you would get one tone being modulated by five of the available operators.

Programming sounds in the DX7 made no sense or followed no logic as far as I was concerned. It was basically trial and error.

The later DX7 models (DX7S, DX7 II, DX7 IIFD) that came later had the option of having something other than a sine wave for the operators to use. This gave more flexibility to programming sounds and then eventually samples were being used that was a digital recording of real instruments that are mostly what you find in keyboards today. Hope this helps!

By the way, I still have a pristine example of the original DX7 in perfect working order. I also have a perfect example of Roland's D50 that was another milestone in keyboards.


supernicd

QuoteProgramming sounds in the DX7 made no sense or followed no logic as far as I was concerned. It was basically trial and error.

That is my experience also.  I also have a DX7, and now tons of software FM synths.  If you just go in and experiment and see what you come up with, you can get some really cool sounds, and it's lots of fun.  If you set out to make a particular target sound, you are likely headed down a road of frustration.  There are some good rules of thumb, like that modulation indices that are whole numbers make harmonic sounds, and those with decimals are inharmonic.  But in my opinion FM is the most difficult synthesis type to program if your intention is to arrive at a particular known sound.

Looking forward to checking out the links Elantric provided to see if there are any new tips in there.
Strat w/ GK-3, Godin LGXT
VG-99, GR-55, GP-10
---------------------------------------------------------------

gumtown

 Visual perception is the key,
most non-musician people listen with their eyes.
With using the GR-55 for a few non-guitar sounds, I have been accused of using backing tracks.   :P
You could even hang the harmonica over your backside while playing your V-guitar rendition, and folks would think you are playing the real harp.

Quote from: Elantric on October 02, 2014, 09:31:49 AM
The old trick we used in the old days was use a real harmonica for the first few notes, then use your "synth" harmonica.

Most folks will think the whole thing was done with a real harmonica.

And these are cheap

Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

Rhcole

It's hard to fake FM with two analog oscillators. The more oscillators you have to work with, the closer you can get, especially as you combine different bits of distortion and other tone-bending processing in different ranges, intervals, and envelopes.

...or you can use FM.  ::)

MusicOverGear

Figured it out. One is obvious: Ring Mod gives a similar metallic clankiness that can be bent toward what I want.

The other thing is better for more extreme FM sound: Mix in Normal Pickups with FX > Pitch Shifter and adjust up the scale for the amount of uncanny metallic overtones.

I am uploading a song right now that uses an FM EP I'm very satisfied with. It will be in the GP-10 Patch Exchange when it finishes uploading.

Rhcole

Look forward to your recording and patch.