The aim of this project is to make my electric guitar fully polyphonic. I have chosen to install the Ghost Modular Pickup System by Graph Tech Guitar Labs.
The piezo pickups come preloaded in a Floyd Rose saddle for an easy installation.
The existing saddles are replaced by the piezo saddles. The piezo connection is then threaded through the cavity of the guitar to the Hexpander board. The DIN 13 jack socket is connected to the Graph Tech “Hexpander Board” that conditions the piezo signals. “The Hexpander Modular Pre-amp features a proprietary harmonic damping system that results in tracking that is unequaled by any other system on the market today, with responsive and accurate triggering.” 
The term “Hexaphonic” is misleading in that it assumes that users utilise the pickup system on a six string guitar. Inventor and Musician, Matthias Grob explains this on his website. “Some say “Hexaphonic”, which is only correct as long as the instrument has 6 strings, so we prefer “Polyphonic” here: Polyphony has its specific meaning in the music history, but the word itself simply means that there are several “sounds” and we understand several “voices” or notes. Of course this is the case for any ordinary guitar, but conventional technology treats all notes as a single sound source – which is often not in the sense of the musician!” 
A seventh pin is provided to allow a user to connect the sum of all the piezo pickups. Given that I am using a seven string guitar, I simply connected a seventh piezo to the seventh pin so that I have independent audio for all seven strings. I intend to mix the magnetic monaural pickups with the piezo pickups. edit; 12/11/2009 The 7th pin (marked with a circle) on the second row of the Hexpander board ceased to function once the Fernandez sustain pickup was installed. Audio for the 7th string could be obtained once again by reconnecting the piezo pickup for the 7th string to the magnetic channel (marked with an M) on the first row of the Hexpander board. My thanks to Morgan Ahoff at Graphtech Guitar Labs for helping to resolve this issue. Here are two early audio examples of the polyphonic guitar system. This is material being developed under the alias of signalsundertests, a project with DJ and programmer, John King:
Polyphonic Guitar Sample 1 Example 1
Polyphonic Guitar Sample 2 Example 2
Thanks to Michael Barkley for his Luthier skills, and to Morgan Ahoff at Graph Tech Guitar Labs for all his direction on this project. The next step is to build a break out box that provides the pickup system with power.
 Graph Tech Guitar Labs. (2009) Ghost Modular Pickup Systems. http://www.graphtech.com/products.html?CategoryID=2. Accessed on 15.07.09.
 Grob, M. (2008) What do we mean by Polyphonic? http://matthias.grob.org/pParad/WhyPolyGuitar.html. Accessed on 15.07.09.