guitar synth

[eeleye]

I've been thinking of getting into MIDI guitar, but all the setups seem to lick the proverbial pouch. Then I had a random idea while fixing a Casio.

The oscillator produces a basic waveform, right? And everything after that is some form of control to turn a "test tone" into a synth. Could a guitar output be "injected" into a synth in the place of the oscillator? I doubt it would replace the MIDI guitar interface, but there could be some cool sounds to be had.

I'm speaking with very little education here, so please:
Corrections? Suggestions?

[blue hell]

For an analog synth you could do that (with appropriate amplification of he guitar signal). For a digital synth the whole process would be simulated by a computer program so there is no physical injection point.

So it depends on what synth you have.

[eeleye]

I have a Korg EMX-1, which is perfectly willing, but I'll go get something else if this is even remotely a possibility. Simple & cheap is better to start.
Chances are, my first attempt will become a pile of solder, as I don't even know what an oscillator circuit looks like.
But hey, God hates a coward, right?

[blue hell]

[eeleye]

Yeah, I've done some extensive playing around with the EMX-1's inputs, and it does allow you to run the guitar or mic through the effects, as well as the filter with LFO. It's agreat unit, but it does not truly use the unput as the oscillator source. Thus, no pitch LFO, no cross mod, etc.
I'll have a look at the link, though. Thx.

[blue hell]

[eeleye]

I'm looking through some synths, and everyone seems to be going digital. All the genuine analogs are supremely expensive. Any ideas?

[Narbotic]

I am admittedly green to this scene, but have had thoughts recently of the same variety. After determining the proper level to boost the guitar to, one would be able to create . . . say maybe a WSG stompbox?

[doctorvague]

I play guitar through my modular rig all the time. I usually use a distortion box on the way in for some gain and for some high frequency content to work with. Usually you need some kind of boost as well to get to modular levels but that can be a stomp box booster or a mixer module with gain, etc.

This is using a DIY LPF filter I built and hitting it with an envelope triggered by a Doepfer sequencer:

http://idisk.mac.com/doctorvague/Public/Clips/Rubber1Gtr.mp3

Here's a longer jam using a LPF filter like a wah-wah using a Doepfer foot controller module interface. The guitar is not mixed up front because it wasn't intended as a demo, just a rough mix of our normal Friday night jam. The second one isn't very interesting till about 3/4 through there are some semi-interesting chirpy harmonics:

http://idisk.mac.com/doctorvague/Public/Clips/0407jamwithrubberfilter1D.mp3

http://idisk.mac.com/doctorvague/Public/Clips/0407jamwithrubberfilter1D-2.mp3

I really like the effect and feel of using synth filters with an expression pedal as you would use a wah pedal. If you set it up right you can have full control of the range of the pedal and the low and high points which is really cool from a guitar-wah perspective. You can also invert it and break up all those pesky brain-foot habits.

FWIW I've done a lot of other experimentation with my Roland guitar synth>MIDI>gate or trigger and it introduces way to much delay (not the good kind) for my taste. I'm still experimenting with another alternative, an envelope follower. In my experience if using an envelope follower to extract an envelope or gate then a clean signal from the guitar would be preferable to distorted (at least to feed the env follower) as distortion boxes square off the guitar waves and don't give the normal attack envelope of the guitar to the env follower to work with, especially if you want that quacky Mutron sound. Hope that made sense.

I don't know anything about directly extracting pitch from monophonic guitar though - never pursued that. In the food-for-thought dept - the Roland VG-88 takes an interesting approach of mangling and twisting a guitar sound into other sounds without directly turning it into MIDI or pitch. Check one out sometime just to see what it does. It's quite different from the normal MIDI-based guitar synth (which always has too much delay for my taste). When I'm talking about delay in these terms I mean the time between picking the note on the guitar and when you (eventually) hear a note.

Check Bugbrand too he's all over the guitar-modular thang. (Love that E-bow trick).

cheers
Phil

[Mohoyoho]

Most synths have an external audio in. You have to remember to have the gate open and the VCA's envelope sustain up. I recently worked on a video featuring the Moog Freq Box (MF-107), and I must say that is a pretty nice device to get your guitar to interact with some synth features. It's very unusual, and despite some of the audio examples floating around the internet, the Freq Box can be quite musical. It's also amazing with a synth; it basically adds another oscillator to your setup.

[zipzap]

i´m planning a bass synth for a friend. Same thing.
There are different approaches, but i also think this could be best:
Boost the signal - generate an cv (envelope follower) - Alter the harmonic content by distortion, squaring, dividing, pll, waveshapers, mixing all those - filter (with foot controll and the envelope follower) - vca to apply (part of) the natural envelope of the guitar/bass to the signal.
THink if trimmed well this might work.

One proplem i discovered is that squaring up the signal can lead to unwanted bursts and clicks when playing a t low level, at the ending of a note, when not playing at all.

I see two possibilitys: Use the vca end the envelope follower as a kind of noise gate.
Or, propably better, use a simple noise gate made out of two antiparallel diodes to gate everything below +-0,3v after the first gain stage.
So the gain has to be trimmed for good results.

Anyone got experiance with this?


I´m thinking about something different too: Add another oscillator.
For ringmod or fm.
Wonder how it sounds if that osc is set to sync with the squared up guitar. Could be quite dramatic!
And if it´s a vco the pitch could be controlled by another footpedal!

[doctorvague]

Zipzap I'm totally tracking with your ideas. Don't have any answers to your questions though. I was just thinking he other day how certain classic distortion boxes tended to really sound square-wave on guitar, more than others. I seem to recall the Fender Blender as one of them. Some had a bit of an octave effect without being a full octave box. Anyway, the more of a classic square wave you can get out of the guitar, the more options you would have using it as an oscillator in a modular - like to sync an oscillator to - which I have not tried BTW. Also might be able to drive a PLL - and other possibilities.
I'm still in early experimentation with this (as you can tell from my demos) but am very interested. I personally am not following the pitch>CV route as I think there would always be a delay as it's finding the note. I'm pursuing more of the track you just posted.
Unfortunately I'm moving across country in a few weeks and am going to have to pack up my DIY for quite a while we live temporary.
Please post your results as I'm very interested in this - and glad someone else is

Idea: Using the Roland hex pickup you can easily build a breakout box for the 6 string outputs (they also make a bass pickup I have as well). Then run that through a 6x env follower, 6x distortion, etc. Basically figure out the signal chain and splitting/distorting etc and duplicate it 6x, one for each string. The hex-fuzz idea isn't new, but combining it with your ideas would be.

Another idea - Guitorgan. The one thing it had was individually wired frets split into 6 sections each. It would be quite a wiring job, but you make each string high-note priority and (with the right circuitry) extract an accurate note CV from each string. Finding a Guitorgan might be more difficult than wiring it though!

Cheers
Phil

[goldenechos]

[doctorvague]

[goldenechos]