In the Part 2 lessons for 3 string CBG, I retune the GDg tuning to ADf# tuning.

This is Open D Tuning because it contains the 3 tone (1,3,5) from the Major D scale (1-D  2-E  3-F#  4-G  5-A  6-B  7-C#  8-D) needed to form a Major D chord.

From low to high the notes are stacked 5-A  1-D  3-F# 

In the lessons, I explain a system of movable chords based on a root note found on each string.

String 3 is based on a movable C chord. (Fret 3)

String 2 is based on a moveable E chord. (Fret 2)

String 1 is based on a movable A chord. (Fret 3)

Understanding this makes it possible to find the same chord in three different positions on the fingerboard.

In the video New Morning Dew, I am in Vestapol Tuning. Most guitarist know this as Open D Tuning (DADf#ad / 151351), although I am tuned a full step  lower to the key of C (CGCegc / 151351). Due to the fact the tones are relative to their respective keys, all the fret positions are the same except that the guitar will sound in a different key.

Notice that the Open D CBG tuning ADf# / 513, is a small part of the full 6 string Open D Tuning D(ADf#)ad. 

The same movable chord system that is used on the 3 string CBG can be applied to the 6 string.

In the opening chord progression I am playing:

C -Root string 3 / Em -Root string 2 / Bb -Root string 3 / F -Root string 1

The simple point is that if you understand the relativity of open tunings, your knowledge can be easily transfered to different instruments regardless of the number of strings.

Banjo: Traditional Bluegrass tuning is gDgbd / 15135 . Even though this the key of G, the same tonal relationships are here: g(Dgb)d / 1(513)5.

4 string CBG: tuned Dgbd this is the same tuning without the high drone string. Note that this is a part of the full 6 string Open G tuning: DG(Dgbd) / 515135. The same moveable chord system applies here: DG(Dgb)d.