A few years ago, while running on a treadmill at the gym (don’t read too much into this), I thought “Of course! Seven-string guitar tuned in major thirds! Same range as Spanish tuning, perfect symmetry, no B-string shift…It’s perfect!” I found a cheap Ibanez solid-body on Craiglist and started investigating the possibilities.
When it finally occurred to me to fire up a Web browser and see if anyone else was working along these lines, I was immediately disabused of any notion of originality: in 1964, jazz guitarist Ralph Patt introduced the system, inspired by his studies with Gunther Schuller to devise a tuning that would make twelve-tone playing easier. (For details, check the terrific Wikipedia article on Ralph Patt and major thirds tuning, and Ralph’s web site.)
The system has its pros and cons, of course. I’m a jazz guy, so can’t really speak to what it offers folk players, classical guitarists or rockers. I think it’s probably fine for blues playing, though I don’t think it confers any special advantages in that idiom.
Pros of M3 Tuning
Symmetry: There’s no B string shift, so there’s only one fingering for a scale or chord, regardless of string set. For any given note, its octave can be found four strings away, on the same fret.
Half-steps between adjacent strings are available without stretching, enabling rich jazz chords without strain.
Chromatic scale in position (no stretch or shift), so more note choices are available with fewer shifts.
Close voicings are easy, as are five- and six-note chords using barre and open strings.
It’s great for jazz: I find that lines tend to skew diagonally up and across the neck. It seems to me that you run out of guitar less frequently, and it’s easier to play long lines without going down some positional rat-hole that requires a sudden and awkward shift.
Finally, my experience is that the things my hands learn from playing M3 guitar seem to make them smarter when playing a conventionally tuned guitar. The training makes them willing to do things that we don’t usually require of them.
To help organize my own thinking and practicing, I wrote a method book, which you are free to download. I welcome any constructive feedback, and am happy to answer any questions I can.
UPDATE: (Jan 2022) I've added a small supplement with some more recently discovered rich voicings and exercises, three simple arrangements, and suggestions for exploring M3 tuning. As ever, feedback and corrections most welcome!
I've created some instructional videos:
...And videos of me playing M3 guitar in a trio setting: