Wish Harmonic generator with level controls for each harmonic

[woodbutcher65]

No, not a synthesizer. Just a means of altering the harmonic mix of an overdriven signal. To have control over its timbre, which depending on the harmonic mix may be more like, to give some examples, a Fuzzface, or a Randall RG80, or a Pearce G1, or a G-K 2100SEL, or....pick an amp with a distinctive overdrive tonality. Because it's the combination of harmonics that gives each overdrive circuit its character, that and also post-overdrive equalization. The goal of this would be to alter the character of the sound of the overdrive/distortion. Not to turn it into a synthesizer. Just to , for example, pull a harsh harmonic out of the sound while retaining sweet sounding harmonics. Or the reverse, if you're seeking a particularly nasty tone.

 

[NY Guitarist]

That I can understand, though I’m not clear on what the desired results are. What you've described sounds like a synthesizer.

Watch the Harmonium video and think of how you could apply this idea using the guitar signal as the oscillator. The roadblock is that while the synth processes each note separately the guitar's notes would have to be somehow broken out in real time and then processed.

I've done work like this with Melodyne, for example where I can change pitch or timing of one note of a chord, but it's a non-real-time process.

Harmonium

Melodyne

 

[woodbutcher65]

NOT looking for a synthesizer functionality. Just the ability to alter the harmonics in an overdriven signal to change the tonal qualities of the overdrive to replicate the overdrive characteristics of any of a number of existing amplifiers, or maybe even come up with a distinctive new overdrive flavor.

If it ended up sounding like a synthesizer it'd be an utter failure at delivering what I'm envisioning.

I hope I don't have to say this again. NO SYNTH.

 

[GlennO]

NOT looking for a synthesizer functionality. Just the ability to alter the harmonics in an overdriven signal to change the tonal qualities of the overdrive to replicate the overdrive characteristics of any of a number of existing amplifiers, or maybe even come up with a distinctive new overdrive flavor.

If it ended up sounding like a synthesizer it'd be an utter failure at delivering what I'm envisioning.

I hope I don't have to say this again. NO SYNTH.

What you are asking for is: real-time individual control over the harmonics, which necessarily requires Fourier analysis of a monophonic signal followed by synthesis of the partials according to the desired harmonics. I don’t understand why it bothers you, but whether you like it or not, that is YES SYNTH .

 

[Rex]

Watch the Harmonium video and think of how you could apply this idea using the guitar signal as the oscillator.

That's a synthesizer, with synth music in the background, explaining how they use harmonics to synthesize a sound. They don't actually show you the adjustments in real time, so you can't hear what effects those harmonics are having. It's just a random tune playing in the background.

 

[NY Guitarist]

Watch the Harmonium video and think of how you could apply this idea using the guitar signal as the oscillator.

If it ended up sounding like a synthesizer it'd be an utter failure at delivering what I'm envisioning.

I hope I don't have to say this again. NO SYNTH.

You missed my point. The guitar is the sound source. You would be generating harmonics from the guitar and that's literally what you are asking to do. If you use a guitar as the sound source it creates guitar harmonics. Think of it, as someone else mentioned, as a pitch shifter, but a very sophisticated one.

I used the synth video as an example of how one could generate harmonics based on the pitch of the sound source but using the guitar sound instead of the synth sound. IT'S NOT A SYNTHESIZER. That's as simple as I can say it, so i won't say it again.

That's a synthesizer, with synth music in the background, explaining how they use harmonics to synthesize a sound.

The synth video shows harmonics being generated. Reread what I'm saying about using the guitar sound INSTEAD of the synth sound.

 

[NY Guitarist]

What you are asking for is: real-time individual control over the harmonics, which necessarily requires Fourier analysis of a monophonic signal followed by synthesis of the partials according to the desired harmonics. I don’t understand why it bothers you, but whether you like it or not, that is YES SYNTH .

Thanks Glenn, well said. I think the confusion stems from my using a synthesizer example to show how harmonics can be created. So yes, harmonics are synthesized, just as any digital pitch shifter does, but it doesn't turn the guitar into a 'synthesizer' (instrument). Sort of a semantics issue at play here I guess.

It was, for me at least, a fun thought exercise.

 

[Rex]

I get that the signal coming from the guitar would be the source of control. but it's still synthesis, and it's still a synthesizer by any definition. Even if it doesn't have a keyboard and it doesn't say "Korg" on the back.

Depending on what mix of harmonics you chose, it could churn out a sawtooth wave or a square wave — traditional synth sounds.

 

[FractalAudio]

Let me go back to the concept in my head.

Take the best sounding overdriven guitar tone you've ever heard. Your personal favorite.
Now imagine if you could individually control the level of every harmonic generated by that overdrive. Second, third, fourth, eleventh...whatever. All harmonics within hearing range. And in doing so, change the character of that overdrive. Make it more "tubelike" or more "solid state", or single ended or push-pull in nature. Be able to, if you wish, complete suppress specific harmonics, or accentuate them.

Of course this isn't a fixed frequency issue, it's a very dynamic process. Guitars don't generate simple sine waves at a fixed frequency. You'd have to write code that dynamically creates the selected mix of harmonics not only for the note being played, but for all the notes and harmonics in the input signal, all at once. And then intermodulation distortion has to be calculated and added in, and yeah, I can see that this is going to require a lot of processing power and I can't even make a realistic guess as to what the DSP code would look like.

For natural sounding (not synthesizer sounding) distortion the harmonics are not static. They change with applied amplitude. How do you propose adjusting something that is inherently dynamic.

Mathematically the best you can do is an adjustable waveshaper where the user can freely define the shape. There are probably already products that do this.

I suggest you do some research on Fourier series, waveshapers, etc. I think you have a fundamental misunderstanding of distortion and harmonic series.

 

[NY Guitarist]

Depending on what mix of harmonics you chose, it could churn out a sawtooth wave or a square wave — traditional synth sounds.

Completely misinformed. Does a pitch shifter give you a sawtooth or square wave? No it doesn't, it give you whatever you put into it just shifted.

Anyway, I tried to offer constructive suggestions but I'll let you guys work it out, lol.

 

[Rex]

Completely misinformed. Does a pitch shifter give you a sawtooth or square wave? No it doesn't, it give you whatever you put into it just shifted.

If you have a bunch of pitch shifters, and you set each one to generate just the right amount of just the right harmonic (you can derive any harmonic by pitch-shifting the source) , you'll get a sawtooth wave. Look up the spectral content of a sawtooth wave, and you'll see what I mean.

 

[NeoSound]

You can pan pitch shifter voices, if you use both blocks you can get four separate pitch shifted paths (+dry signal). You have four drive blocks to feed the separate pitch voices into (or feed them into the shifters) and an amp block to feed the dry signal. Plus an additional amp block for? This would let you have a crude way to test your idea...?

 

[mr_fender]

Completely misinformed. Does a pitch shifter give you a sawtooth or square wave? No it doesn't, it give you whatever you put into it just shifted.

Anyway, I tried to offer constructive suggestions but I'll let you guys work it out, lol.

Pitch shifters don't generate harmonics of the input signal. They shift the frequency by manipulating the playback rate of the delay line used to capture the signal. Think of it kind of like an analog tape or vinyl record. If you move the tape or record past the head/needle faster, the resulting pitch is shifted up. If you move it slower, the pitch is shifted down. It has nothing to do with harmonics.

 

[Rex]

Here's another complication: the concept of harmonics is meaningless unless you're starting from a pure sine wave, and guitars don't produce pure sine waves. Even a single ultra-clean note contains the fundamental plus a series of harmonics. How do you derive the harmonics of all that? You break down the guitar signal into its component frequencies (there's the Fourier analysis that @GlennO spoke of and @FractalAudio alluded to). Then you calculate the desired harmonics for each of those frequencies.

Either that, or you strip the guitar note down to its fundamental frequency (or frequencies, if you're playing more than one string), and calculate the harmonics for that. That's going to wound way synthy.