C.F. Morrison Em13 guitars are 8 string acoustic and acoustic/electric guitars built to support the Split Dorian Tuning. The Split Dorian Tuning is a new tuning derived by Chuck Morrison. The purpose of the tuning is to enable the playing of chord structures that are exceedingly difficult or impossible to play on standard guitars. A byproduct is an instrument and tuning that lays bare the fundamentals of music theory to the knowledgeable musician.
The split Dorian Tuning consists of every note in the Dorian mode, although not in strict ascending order. The E Dorian scale is E, F#, G, A, B, C#, D, E. From the lowest pitch string, the strings are tuned to the following notes in order: E,G,B,D,F#,A,C#,E. When looked at numerically, it is tuned thus: 1,3,5,7,9(2),11(4),13(6),8(1) and covers two octaves. The two E strings are tuned to the same pitch as the outer strings of the standard six string guitar. Looked at as intervals, the strings are tuned to alternating minor and major thirds; m3, M3, m3, M3 etc. Since the result is stacked thirds, lots of chords are available as partial barre chords.
When looked at as a chord, the split Dorian tuning is a full Em13 chord. When the 8 open strings are played in four note groups the following chords are evident:
7,6,5,4 G Major 7
5,4,3,2 D Major 7
8,3,2,1 A Major
These are all root based inversions. except for A Major, which has the 5th (E) in the bass.
Aside from an adjustment period to deal with 2 extra strings and different fingering patterns, the tuning is very easy to use for playing and arranging chord melodies.
If you understand what I’ve written above and think it might be worth trying out, using the tuning with a six string guitar is a great idea. One only needs decide on which two strings to omit and get some new string gauges. I recommend the following string gauges for steel string guitars:
E G B D F# A C# E
.054″ .045″ .040″ .032″ .026″ .020″ .014″ .0115″
.053″ .039″ .012″
The options for using six strings are:
Omit the bottom two strings (E and G) – B, D, F#, A, C#, E
This will need to have lighter gauge strings except for the E.
Omit the top two strings (C# and E) – E, G, B, D, F#, A
This can be done now without changing string gauges, as all but the E
string are tuned lower than standard pitch, however the higher the
string – the lower the tension will be, which may not produce a good
Omit the outer strings (The E strings) – G, B, D, F#, A, C#
With this one the D string remains as in standard tuning but those
below are tuned higher and those above are tuned lower.
Each option has it’s down side, which is why I chose the 8 string version going forward. It also encompasses the entire range of the standard guitar. No one should consider purchasing an 8 string version if they haven’t tried it out on six strings first and see the benefits of all 8 strings.
There are numerous files displayed below that show ‘lanes’ of strings. These are 4 (or 3) string groups that provide a reference point for a group of chords. I hope it is somewhat self explanatory. By thinking in terms of these lanes, navigating 8 strings becomes much easier.MajorChordGrids-8-MajorLanes