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Guitar-like midi synth controller


squeal
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how about an inductive fretless?

Take a very thin, hard conductor (0.1 mm, steel maybe?) and wind it around the board, in a spiral from top towards the bridge. that'll create an inductor. all the strings get connected to the end of the inductor at the very top. when you touch the string to the bare coils, you bypass turns. The strings will be tested one by one in a time-division-multiplexing manner. Less inductance = higher pitch.

method 2.

you could use the way conductors work for RF electric signals you could perhaps check the lenght of the string before that touches the board. It'll have a resonant frequency. etc etc etc

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I'm afraid I still don't understand what's wrong with the vhs tape (or other resistive strip) method.

Each string is isolated, and a separate strip of resistive material is glued to the neck directly under each string. The strip is part of a voltage divider which sends a voltage depending on where you finger it. ;)

The only issue I can see is that vhs tape has a resistance around 1Mohm per foot, and the resistance between my fingers is also around 1Mohm, so the neighboring strings could mess up eachother's pitches.

Now if I could find a material with a much lower resistance, say 10Kohm/foot, then the resistance between my fingers would be negligible. 

Or I could play with rubber gloves on.......

But seriously, is there something I'm missing here?

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...

Or I could play with rubber gloves on.......

But seriously, is there something I'm missing here?

hehe, do you own rubber gloves or rent them?

really, there would be little lost by testing this idea

just try a quick one-off and you'll know for sure...

btw, i thought of a way to make the fret switch idea work.

i realize you are not interested in that approach, but i'll

post it anyway for the hell of it, since it came up in this thread.

put an analog in on each fret, and a resistor ladder between the

strings with a log(2) "taper" and 5v on one end, gnd on the other.

set up the values so you can ignore the bottom 4 bits and just use

the upper 6. using 1% resistors, you might not need trimmers.

ex  5v - 16.5k - 8.2k - 4.1k - 2k - 1k - 499 - gnd

[hmmm, check that - maybe need 2n-1 instead]

now for each fret (each ain), each of the top 6 bits tells you if the

corresponding string is down.  since at least 2 frets will be contacted

for each string that is pressed down, you would need to check in code

for the highest fret (ain) for each string...

(this is related to the way kim flint designed the foot control for the

echoplex digital pro so that only one 1/4" cable is needed - very clever)

bending would not be tracked, but at least would not destroy the surface...

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hehe, do you own rubber gloves or rent them?

really, there would be little lost by testing this idea

just try a quick one-off and you'll know for sure...

btw, i thought of a way to make the fret switch idea work.

i realize you are not interested in that approach, but i'll

post it anyway for the hell of it, since it came up in this thread.

put an analog in on each fret, and a resistor ladder between the

strings with a log(2) "taper" and 5v on one end, gnd on the other.

set up the values so you can ignore the bottom 4 bits and just use

the upper 6. using 1% resistors, you might not need trimmers.

ex  5v - 16.5k - 8.2k - 4.1k - 2k - 1k - 499 - gnd

[hmmm, check that - maybe need 2n-1 instead]

now for each fret (each ain), each of the top 6 bits tells you if the

corresponding string is down.  since at least 2 frets will be contacted

for each string that is pressed down, you would need to check in code

for the highest fret (ain) for each string...

(this is related to the way kim flint designed the foot control for the

echoplex digital pro so that only one 1/4" cable is needed - very clever)

bending would not be tracked, but at least would not destroy the surface...

good idea! i think even better than my time-division-multiplexing idea where you check each string separately.

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set up the values so you can ignore the bottom 4 bits and just use

the upper 6. using 1% resistors, you might not need trimmers.

ex  5v - 16.5k - 8.2k - 4.1k - 2k - 1k - 499 - gnd

[hmmm, check that - maybe need 2n-1 instead]

that should have read 2^n - 1, which isn't quite right anyway

thought a bit more about it and that list is missing one resistor

and it needs to be offset by 8 (or 7) to get into the middle range of the

4 bits we are discarding (so errors in resistance either way won't break it)

so according to my calcs, R values should be in ratios of:

{1.5,1,2,4,8,16,31.5}

which means more like:

gnd - 154, 102, 205, 412, 825, 1.65k, 3.16k - 5v

strings go between the resistors of course

ok, real world test is needed before any more math geekiness.

if nobody else tries this i will eventually get around to it.

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  • 2 weeks later...

Would anybody be interested in an idea of got for a guitar based MIDI controller?

I'm thinking of a mono-synth, built into a guitar with the frets and strings forming the controller.

Each of the frets will be wired to a DINx4, and will form a matrix with the six insulated strings. The controller would then have highest note priority. I'm thinking that a single DIN and core could be used to form the basis of the controller.

Each of the strings would be connected to a pin on the DIN , and each of say 22 frets would be connected to their own pin. The core software would then be able to see which string was being connected to which fret number, and trigger the corresponding MIDI note.

The clever bit would be the gate detector, which requires the use of an analogue input to the core. This would look for a signal from a guitar pickup (normal pickup). When the signal is above a certain voltage, that triggers a note-on signal, and when it falls below this threshold, it triggers a note off.  Obviously it would be trivial for this to allow for pitch bend when a note is played before the previous note has decayed. I guess the gate control could be disabled so that when a note is fretted, it will sound without the need for a string to be played.

So, what do you guys think of my idea?? I would like to apply it to a SID synth, built into a guitar, now that would be cool! I'd be willing to test build a the hardware (I am an amateur luthier), but software is a non-starter for me.

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you´re right, the frets would need to be segmented, too  I missed the part that even while you can wire it up as one (after the diodes), you still need a diode at every single contact point. So this would be a lot of mechanical work. But with separated frets and bridges, it would at least work.

I'm not sure what the affects would be without separated frets  :(

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the "switches" would interfere with each other...

you will still get interference if fretted strings are bent onto the same fret segment

(i think, with the way i play, this would happen often)

Yes, I think no matter the method used, it wouldn't be as simple as just playing it like a guitar (although very close), it would take some practise.

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As I said, if the controller was given highest not priority in MONO mode, then single frets would be no problem at all. Having six mini frets sounds to me like it somewhat overcomplicating things, and is not really necessary. I'm not sure that you'd be able to play it polyphonically anyway, since your fingers may conduct, inducing glitching.

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doesnt the guitar plays the note as soon as you push a string to a fret?

Wouldnt it be more senceful if you built a new pickup with SIX seperate outputs (like 6 mini pickups in one case with sepearate ouputs for each string)?

Then ..... Would it be possible to add a "gate" for every single string with the 6 outgoing voltages of the pickup?

So you could play chords with empty strings or pluck them. You could get polyphonic output and get velocity values for EACH string.

The guitar wouldnt respond on your fingers until the certain string(s) got hit.

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I made a start on the software theory last week.

-AIN input increases by ## very quickly, send note on

-AIN falls below ## - send note off

-The notes that get played are calculated when your fingers touch the fret board. But the notes don't play until there is enough 'loudness' on the pickup.

-Hammer on's, pull off's and slides are can be fairly easily accounted for by checking if the string is already playing a note, and swapping it the new note.

-A fret 'registry' can be used to keep a list of active frets. Highest fret in the list wins. This means you can change the fret below the current used fret, and pull off to play the note below.

Really the basics of the software side are not that complicated,

At least from the software point of view:

-it'll be polyphonic

-it'll be velocity sensitive (although it won't decay like a guitar string).

-Guitar strings will need to be 'hit' to play a note

... I should have an application with basic functionality by the end of the week (although completely untested).  ;D

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Hey guys - I just found this:

SUB-COMMANDER Guitar Synthesizer

Available as a PCB from Ray Wilson's Music From Outer Space

... but there's plenty of info there if you wanted to build your own  ;D

Introduction

/By the time you complete this project you will have built:

A guitar sub-octave generator

A guitar to gate & trigger generator

An audio mixer.

Two AD/AR generators.

Two Triangle wave LFOs.

A 12dB/octave lowpass VCF (Voltage Controlled Filter)

A exponential response VCA (Voltage Controlled Amplifier)

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I'm almost done building the Subcommander right now!  I am extremely interested in guitar-synth or guitar-to-midi type controllers.  I will post some videos when I am done building it.  Also check out Ray Wilson's Sound Lab Mini-Synth... he offers schematics for a guitar-trigger add-on.  This sounds like a great project -- I will gladly build one once a successful prototype has been made.  I'm almost done with a 30" ribbon controller that i plan to play with a strap, like a "guitar". 

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My 2c.... This is the only way to fly:

                              ___     _
N||==========================| L |---|B|
U||==========================| D |---|B|
T||==========================|_S_|---|B|

B = Bridge, NUT = ,well, nut...

LDS = Laser Distance Sensors. 6 of. Mount in the body facing up the neck to measure 'string' length.

--- = Guitar strings tensioned through peizos or pressure sensors or something, for actuation.

I hate to think of the work and money involved... if the LDS can even be made to fit in a space that small....

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