I've been thinking about this arrangement recently, partly after seeing Michael Manring live, and partly from reading about Adrian Legg's custom guitars. Basically, the idea is to put a detuner key on every string, and set it so in the 'up' positions, the guitar's tuned to DADGAD, and then each detuner tunes its string down an additional tone, allowing the following tunings...
Kaki King's CGDGAD
DADGAD down a whole step
'Double Drop C': CGCFAC
Michael Hedges' DADGAC
Open D Minor
An Adrian Belew-style DGCGAD
...And those are just the ones I can think of off the top of my head, although the main one's I'd use would be DADGAD, D standard and Drop C.
Are there any detuner keys that would fit on a three-a-side headstock?
Detuner keys need a lot of room to move... putting more than one or two of them on a headstock would be a challenge.
Other options would be a blocked Floyd with an EVH D-Tuna on every string, or consider the Hipshot Trilogy bridge, which is designed specifically for this kind of application.
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