Major thirds tuning
The M3 is tuned in fourth fret all the way up. You can choose whether you want to use the major third tuning on a 6-string guitar (M3-6) or a 7-string guitar (M3-7). From low to high the open strings are E-Ab-C-E-Ab-C on the M3-6 and with an additional high E on the M3-7. Since the top and bottom strings are E's two octaves apart on the M3-7, the range of notes at your disposal is the same as on a 6-string guitar in conventional tuning (C6) whereas you are lacking four semitones in the top with the M3-6. A crucial property of the M3 is that the symmetric tuning causes runs and chords to form highly structured patterns on the neck. There is no equivalent to the exceptional interval between the 2nd and 3rd string (four semitones as opposed to five semitones between all other pairs of strings) that breaks the symmetry on the C6.
Advantages
- The M3 is symmetric. A certain pattern, or chord shape, looks the same everywhere on the neck, regardless of the position and the string group.
- On the M3 octaves repeat. Since 3 times 4 is twelve, there is one octave between the same frets three strings apart. You can make chord inversions just by moving one finger three strings up or down! The fourths tuning, which is used by some guitarists to create symmetry, does not have this property.
- On the M3 you play fresh sounds. The M3 is very different to play mechanically from the six-string in conventional tuning so you won't be able to follow the same line of thinking as 99% of the world's guitarists even if you would like to. For this reason it is easier to figure out things that sound new and fresh.
Disadvantages
- You start from scratch. In the beginning, the instrument is totally impossible to play. It probably takes between three and six months before it starts to make sense, and there is a good chance that at some point you wont be able to play either the C6 or the M3.
- You throw away part of the tradition of the guitar. A lot of the things you hear guitarists play on records are very hard to execute on the M3, and there are no tutorials that can help you to learn those. Books that include fingerings and tablature are useless so you have to work quite hard, particularly in the beginning, in order to develop your own musical vocabulary.
- You have to make an effort to find strings, and with the M3-7 equipment in general. The selection of 7-string guitars is severely limited, not to mention acoustic guitars and midi-gear. Strings in the right gauges are not readily available, and you will most likely have to buy them on the internet.
M3-6 versus M3-7
6 strings or 7 strings, what should it be?
- Range of notes. With the M3-6 you are without the high-E string so you have to get used to shifting high up the neck. If you like the sound of the high notes well above the 12th fret on the first string of the C6 you will be struggling with the M3-6.
- Physical feel. The highest string on the M3-6 is thicker than on the M3-7, giving it a darker, heavier character, but then on the other hand the fretboard is narrower which makes it more manageable.
- Picking and playing chords. You can play big chords on the M3-7 but you also have to make an effort to stop the open strings from ringing. In addition you have to be careful about attenuating higher strings when you 'swing through' a chord with a pick. On the M3-6 picking is generally easier and it is often possible to put the top note of the chord on the top string.
- Equipment. I have to admit the main reason I have returned to 6-string guitars after ten years with the M3-7 is because I have got frustrated with how hard it is to find gear. If you are a jazz buff with a custom-made 7-string archtop, and that is all you ever play, then it is not an issue but if you are looking for a strat you are in trouble.