How do guitar synthesizers work?

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How do guitar synthesizers work?

Post by Bitexion » Wed Apr 15, 2015 6:31 pm

I was watching this BOSS SY-300 video, and kept wondering how it actually works.
How does the synth know what pitch you are playing on the guitar neck? And how does it work polyphonically even?
I've seen people play strings chords on these things just plugging a guitar into it. So no extra gear is needed. How's it work?

Guitar synths seem to be a niche in the synth world we don't hear much about, probably because it strays into the "cool guitarists" crowd.


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Re: How do guitar synthesizers work?

Post by c-level » Wed Apr 15, 2015 6:41 pm

a bit incensed that i went and bought an old GK-2 and GR50 80's rack guitar synthesizer, mostly to drive midi out and use as a controller. then a day or two later, roland goes and releases this unit which doesnt need a special pickup... FFS....

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Re: How do guitar synthesizers work?

Post by tim gueguen » Wed Apr 15, 2015 11:41 pm

I'm wondering how it works as well. In the past a guitar synth that let you plug in an unmodified guitar was strictly a monophonic affair, because chords would confuse the circuitry. The old Korg X911 was an example. A polyphonic guitar synth required a hexaphonic pickup, with an individual pitch detecting circuit for each string. That's how c-level's newly acquired GR50 works. The other option was an instrument with wired frets, where the pitch was determined by which fret you had the string(s) pressed against. That setup pretty much limited you to a custom made instrument or controller, as modifying an existing instrument to do that would be too complicated and expensive.
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Re: How do guitar synthesizers work?

Post by meatballfulton » Wed Apr 15, 2015 11:49 pm

Until now, polyphonic guitar synths used so-called "hex pickups" to sense each string individually.

This unit probably takes advantage of the technology that showed up a few years ago in tuner pedals that could detect the pitch of each string simultaneously. A drawback of that approach is it is no longer possible to map individual strings to different sounds.

It'll be interesting to see how well it can track the pitches with bends and sloppy playing. I wonder if it will be able to track bass guitars at all.
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Re: How do guitar synthesizers work?

Post by GuyaGuy » Thu Apr 16, 2015 5:42 am

Usually not very well.

:drums:

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Re: How do guitar synthesizers work?

Post by Bitexion » Thu Apr 16, 2015 5:54 am

And now they've managed to do all that through a simple jack plug. No extra stuff. Boggles the mind. I'm genuinely curious about the inner workings.

So the old guitar synths did need extra equipment strapped onto the guitar to detect pitch, just as I thought.

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Re: How do guitar synthesizers work?

Post by piRoN » Thu Apr 16, 2015 7:06 am

It'd just be doing a bit of FFT analysis. Convert the audio from time domain to frequency domain, run an algorithm that picks out the fundamentals present in the spectrum, then interpret it into MIDI data. With the processing power available these days, it's not a particularly difficult problem.
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Re: How do guitar synthesizers work?

Post by Bitexion » Thu Apr 16, 2015 3:09 pm



In this new demo vid you clearly see it's bending notes like it should, responding to pulls, slides and picking.
It's like every string has its own pitch "wheel". Pretty wicked. A very decent video of various presets.
Thankfully they've recorded from the mixer output so there's no outside interference
Wish I could play guitar like that even.

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Re: How do guitar synthesizers work?

Post by Aaron2 » Fri Apr 17, 2015 4:51 am

As a longtime guitar player, I was also intrigued by this video. In essence, doesn't this mean that -- in this synth at least -- the guitar is acting like a keyboard MIDI controller?

It's pretty cool when you think about it. If you're a guitar player with no keyboard skills, who still wants a synth in his or her rig, then this might be the answer.

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Re: How do guitar synthesizers work?

Post by Bitexion » Fri Apr 17, 2015 12:19 pm

Seems so. It responds perfectly when he pulls or bends the strings while playing like a pitch modulation wheel almost.
Very clever stuff.

I'd assume older guitar synths didn't respond like that? I don't know how the synth would detect that I'm pulling a string to bend the pitch on a note?

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