MIDI guitar idea

[gmeredith]

I've been thinking about building a guitar-type MIDI controller for a while, but wanted it to be a bit simpler than the full-on commercial Roland type designs, yet not like a keytar sort of thing. I've seen some designs like keytars that people have made, which are basically a gutted synth, and press-switches up a neck like a guitar fretboard, which are pretty cool, but I was thinking of something more guitar feel rather than press-switch feel when you play it.

Way back in the 80's I think I remember there being one which worked by the frets on the guitar neck being switches (Casio DG-xx?), so when you played a string, it pressed the switch for that note, and was then simply a key matrix bank of switches like in a synth.

I started to think about it and realised that you perhaps didn't need even switches - you could use the string and the fret as a contact switch in themselves - with the strings being the 0V common rails in the matrix, and the frets being the individual contacts for the CV or matrix note signal. You would need to cut and divide the frets into 6 separate mini-frets, so that each string would work separately.

But say, you made a "1-string guitar" as a proof-of-concept experiment. Then all you would need to do is gut an old cheap MIDI keyboard and connect the "fret" side of the key contacts to the frets. Now, you would rout the string to a contact switch near the guitar bridge that you tap or "pick" to close, and the other side of the switch then goes to the common matrix key connection on the keyboard. Alternatively, instead of gutting a synth, you could make a simple PIC MIDI board that sends out MIDI notes when switches are pressed

You would play it by pressing down on the string for a note, but unlike a keytar, it does not sound the note at this time. You have to "pick" the bridge switch or tap it for the note to then make the sound, more like a guitar action. Seeing that you're then simply triggering a synth, it would also send MIDI notes out to another synth, module, sampler, etc.

It would not have velocity sensitivity, nor pitch bend response to a "bent" string or whammy bar bend, like the real guitar synths do. But it would not suffer from note "tracking" problems or note delay, like the real guitar synths do. And would be easier and cheap to make.

Any comments on this idea? Maybe this could be a joint electro-music project!!

Cheers, Graham

[gmeredith]

I also just realised that you could also use it to control an analog synth with CV inputs, where each fret has an adjustable trim pot resistor and the string/fret acts as a switch to a CV +5V DC supply, plugged into an analog synth CV input such as an SH101. You tune each fret's trimpot until you get the correct tuning for each note. Then you have the "pick" switch set up to pass a gate signal to the synth's Gate input, and there you have it - a simple non-MIDI guitar controller of old synths or DIY synth boards!!

Cheers, Graham

[LukeDI]

Am I reading this right, are you essentially talking about six parallel ribbon controllers? Because that sounds great.

As a bit of input (ha,ha, pun not intended) you could probably implement some sort of a whammy bar by hooking one up as a pot/fader etc that caused a dip in the overall voltage output.

[gmeredith]

Basically, yes! The frets simply create "fixed" increments of control.
Whammy bar would be very easy to implement, as you said, for an analog setup. The "overall" pitch pot would simply be connected to the common line (the string).

Cheers, Graham

[Uncle Krunkus]

Instead of separate trimmers for each fret, it's alot better to connect each fret to a resistor chain and run a constant current source into it. As in Ray Wilson's Single Bus Keyboard to CV/Gate controller.
http://www.musicfromouterspace.com/analogsynth/keybrdcontroller.html
This is what I want to use for my Slide controller.

[gmeredith]

Thanks, Uncle for the circuit! That seems to be a good way to do it. I like his synth board, too - that would be a neat size to build directly into my guitar controller.

cheers, Graham