[sdiy-interim] MIDI guitar, the hard way

Mon Mar 26 17:53:38 CEST 2007

We had partly the same idea about building a guitar midi controler..
I'd thought (like you) to use a matrix of strings & frets
for notes but the analogy stops here.
The frets are not cutted but standards.
For the strings bending & strumming here is my idea:
I'll explain for one string (other 5 will use about the same scheme):
Take the string and attache it to the neck's head using machine heads
or whatever to bend it but not very much..! The other end is where
the bending & strumming trick resides. You take the string inside the 
guitar rolling it on a small pulley and glue the end of
the string 90degrees over a small piezo sensor going across a small spring
to
minimize the hit strentgh. Again this assembly needs very little
tension to work. Then when you hit the string the piezo sensor
doesn't hear but 'senses' the string tension variation giving
an attenuated waveform that is the string volume envelope.
Instead of fixing piezo sensor to the body directly you
hold it at the cursor of a small slide pot at 50% position rest.
So when you bend the string the slide pot follows the finger movement
and gives (if you like) a DC control voltage..
Of course another small spring will retain the pot cursor
at 50% at rest.
This is just an idea.
I hope I'm clear here..

Jean-Pierre Desrochers

-----Message d'origine-----
De : Gorka Garcia [mailto:torpedo at demadrid.com]
Envoyé : 26 mars 2007 11:11
À : synth-diy at vermine.org
Objet : [sdiy-interim] MIDI guitar, the hard way

So... Now for a crazy idea that hopefully I will be able to work on whenever
I finish the other 20 projects in the list:

I have this korean made Les Paul style guitar which I want to become
something useful. I thought about different artistic ways of using it and
finally I realized it was born to be a MIDI guitar controler, but not the
usual MIDI guitar with expensive Roland pitch to midi hardware. My thought
was to connect every fret and every string to an AVR/PIC microprocessor,
creating a matrix of switches between strings and frets. That by it self
will make of my guitar a pretty cool synth controler (I know, no string
bending... oh well) however, I will also like to be able to sense individual
string strumming. I though about it and the only solution I found is using
an Hex pickup (magnetic or piezo). Can you guys think of another solution
for detecting individual string strumming? hopefully something DIY and
cheap? Once the guitar/controler is finished, it does not necesary have to
sound right when the strings are strummed.

Would something like this work (from Dave_B in the diystompboxes forum):
http://davebales.com/me/stompboxStuff/hex_pickup.jpg

Notes from Dave_B:
"Could it look something like this?  I left out the wires and guitar strings
for clarity.  The white and gold part is the cut piezo, the black part
underneath is foam rubber or something similar.  I've seen articles about
glueing whole peizos to guitars for pickups (and tried with some success a
long time ago).  If you put these close to the strings would it be enough to
keep them from triggering notes from adjacent strings?"

Have in mind that I am not expecting to capture sound out of the piezos,
only the amplitude of the strumming.

Thanks,

Gorka

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