[sdiy] pitch tracking / guitar synths

[Don Tillman]

   > Date: Mon, 19 Dec 2005 20:52:27 -0500
   > From: harrybissell <harrybissell at prodigy.net>
   >
   > > One thing I could never figure out is why the hex pickups are
   > > always located so close to the bridge.  I would think that
   > > would accentuate the harmonics.  Anyone want to give me a
   > > lesson?
   > 
   > There is a really neat applet over at Don Tillman's site that
   > shows the effect of pickup position.  

Over here:
http://www.till.com/articles

   > One thing is... the pickup covers a narrow range of the string
   > length.  Picking a note somewhere along the sting will create a
   > series of nodes (zero vibration) at points related to where you
   > picked.  

Yeah, a pickup near the bridge will have a much more consistent
waveform and harmonic spectrum as you play notes up the neck.  Pickups
located near the neck will generally have more fundamental, but the
harmonics will be changing all over when you play notes up the neck
and the harmonic nodes approach the pickup.  That's part of why
electric guitars sound so great, but it's bad for pitch extraction.

   > A piezo would probably work well also... that point HAS to be a
   > node, but its sensing pressure at that point.  I have never tried
   > a hex piezo pickup.

A piezo gets an awful lot of second harmonic.  A piezo senses pressure
and the pressure on the bridge increases both when the string swings
up and when it swings down.  Piezos also get a dc thump for each note
picked.

  -- Don

-- 
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com