The 3rd Rail ( The G & B Strings ) Part 2

What's the best way to think of the 3rd Rail? How can you avoid hitting a wrong note when you move across it? Can't the guitar just be tuned so all the strings have the same intervals between them?

Actually there is a school of thought that a uniform tuning is the solution. Some tune the guitar to 'All 4ths' (E A D G C F) in order to avoid the issue of compensating for the odd interval. But - as stated in the previous post - most guitarists continue to use the standard E A D G B E tuning because it (probably) offers the best overall set of musical possibilities and because the vast majority of resources are available to guitarists in standard tuning. If you've found advantages to other tunings, more power to you. But if you are interested in getting the most out of standard tuning, then you'll want to come to terms with the 3rd Rail.

Think of it as a small hill. When you ascend from the 3rd to the 2nd string, you shift up a fret. When you descend from the 2nd to the 3rd string, you shift down a fret;

Because the interval of a Perfect 4th (W-W-H) is one half-step larger than a Major 3rd (W-W), shifting up one fret when crossing from the 3rd to the 2nd string will produce a Perfect 4th, while moving from the 3rd string to the 2nd string on the same fret produces a Major 3rd. Since there is a Perfect 4th between all the adjacent strings except the 2nd & 3rd, you can think of the Perfect 4th as the 'default interval' when crossing strings. So, when you cross from the 3rd to the 2nd string, think of a Perfect 4th as the norm. To do this, you only need to remember to shift up a fret when you go from the 3rd to the 2nd string, and go down a fret when going from the 2nd to the 3rd string.

Try playing all the notes on the 5th fret one by one from the lowest string to the highest; A - D - G - C - E - A. These are all 4ths except C - E, which is a major 3rd. If you were to play a series of 4ths starting from the same note, you would play the notes; A- D - G - C - F - Bb. Below is notation and tablature for this exercise;

Think of the 'Same Interval' sequence above as the default path for crossing all six strings.

Below is a diagram showing all the natural tone (key of C) Perfect 4ths on the fret board between adjacent strings, connected with green bars;

Notice that the diagram is divided between the upper four strings and the lower three strings. This is to emphasize the symmetries within these groups. Below are separate diagrams for each string group;

Upper String Group 4ths

Lower String Group 4ths

There are two notes on the fret board which are not part of these adjacent string 4ths; the F on the 1st fret of the 6th string, and the B on the 7th fret of the 1st string.

Also, within the Upper String Group, the F on the 3rd fret of the 4th string is isolated from the 4ths, but is a counterpart to the 1st string B. Similarly, the 4th string B in the Lower String Group is a counterpart to the 6th string F.

The interval from F to B is an Augmented 4th (W-W-W), which is a half-step larger than a Perfect 4th (W-W-H), so these two notes do not align when they are in adjacent string/fret positions.

Remember that starting from the middle (5th fret) and moving in both directions from there is preferable if you want to really absorb the symmetries.