Starting in 2009, during my time on the IRCAM cursus, I began writing working with and writing for the hexaphonic guitar: an electric guitar fitted with a hexaphonic pickup that sends out a separate signal for each string. This divided pickup technology has been used extensively in MIDI devices, to drive guitar synths, but my approach works differently: I use the direct signal from each of the six magnets on the pickup.
In Max, I then built a series of hexaphonic effects that are capable of applying different treatments to each string: a polyrhythmic tremolo for instance, a six-voice wah-wah effect, an overdrive with different levels of distortion on different strings or a dynamic delay that transforms a strummed chord into an arpeggio or a fingerpicking pattern. An automated attack detector, applied to each string, allows a pedal-steel “fade in” to also be heard polyphonically, as if each string has its own volume pedal.
Most importantly, I use the hexaphonic pickup to turn the guitar into a flexible microtonal instrument. Using a phase vocoder, the pitch of each string can also be transposed independently, either statically, for “virtual retuning” or dynamically, for glissando effects.
Finally, each string can be independently spatialized as well, given its own position or, using IRCAM’s Spat system, its own 3-D trajectory. In my concerto Westering, a four-speaker setup surrounds the audience, and the live electronics control the pitch, timbre, and movement of several independent layers of guitar sound in real time, sending the strings swirling around the audience.