Major thirds tuning

The M3 is tuned in fourth fret all the way up so from low to high the open strings are E-Ab-C-E-Ab-C. 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 of the conventional tuning.