The Third Rail (The G & B Strings)

What happens between the 2nd & 3rd strings on the guitar ... the G & B strings? There's a long and complex history behind the tuning of the guitar, which we won't go into here ... (google it) ... but to say that at some point the decision was made to tune the 1st & 6th strings to the same note, two octaves apart, and that those strings would be tuned to E. Because there are 6 strings on the guitar, there is no way to tune them all to the same interval and still have the same note on the highest and lowest strings. If most of the adjacent string pairs are tuned to Perfect 4ths, one of the pairs must be tuned to a Major 3rd. That major 3rd falls between the G (3rd) string and the B (2nd) string in standard tuning;

The result of this tuning is that scale patterns and chord forms are broken into various forms depending upon whether or not they cross between the oddly tuned strings. It's a compromise which makes barre chords possible, and it actually makes certain chords in the upper strings easier than they would be were the strings all tuned to 4ths. Of course not everyone accepts this tuning compromise, and there are numerous alternate tunings for the guitar. But the vast majority of guitarists are willing to work within the boundaries of the EADGBE or P4th - P4th - P4th - M3rd - P4th tuning.

In Fretography, the Major 3rd interval between the 2nd & 3rd strings in called the 3rd Rail. The 3rd Rail is a landmark on the fretboard map. It is a juncture – a turning point, or set of turning points. If you think of it the right way, it stops being an obstacle and becomes a useful navigational tool.

Remember that the 3rd Rail is the middle latitudinal axis of the upper string group's symmetry;

Any tonal interval occurring between any other two adjacent strings will be a different shape if it spans the 3rd Rail. For instance; a major 3rd played between the 2nd & 1st, 4th & 3rd, 5th & 4th or 6th & 5th strings will be a short diagonal, spanning two strings and two frets, while a major 3rd spanning the 3rd Rail will cross between the strings in a single fret position;

Compare the sound of the major 3rds in the upper string group (light blue). They are all the same pitches. The dark blue diagonals in the lower string group are an octave lower. All the major 3rds in both octaves are the same shape on the fret board except the one in the 3rd Rail.

There are three single-fret major 3rds in the 3rd Rail in the key of C: The G major 3rd of the open strings (and 12th fret), the C major 3rd of the 5th (and 17th fret), and the F major 3rd of the 10th (and 22nd fret). The symmetry of these positions is shown below;

These three fret positions are the three axis positions, which are indispensable in navigating the fret board.

Next post; The Third Rail - Part 2.


All contents of this blog are © Mark Newstetter