Creating a "6 finger" guitar – reference request on how to create a UI for a guitar that supports more than 5 degrees of freedom
There have been a lot of developments in guitar to stretch the capabilities of the instrument from amps, pedals, multi-string approaches, fretless microtonal varieties, etc...
Fundamentally it seems there is a limitation the majority of humans face which is that there are usually only 5 fingers on their hand touching the neck of the guitar from which to form chords.
Has there been any research done on how to easily, and smoothly give a higher number of degrees of freedom for picking specific notes other than fingers pushing down on strings?
Some ideas I had:
Engage other muscles, say the toe by standing on a pad which tries to map different toe configurations to certain pre-programmed chords, or individual strings
BCI: theoretically we could forego any human limitations if we can engage the brain directly
My Question Concretely:
What are some documents about this topic/and or does anyone know of a canonical solution that has been created?