Disincarnate,

It's a very fundamental device in playing music. It's created by taking the fifth note of each scale and placing them clockwise on a circle. So, starting with "C" on the top we find the fifth note in the "C" scale. I-C, II-D, III-E, IV-F, V-G, VI-A, VII-B. So we see that "G" is the fifth interval from "C" so we place it on the circle. Next we find the fifth note in the key of "G". I-G, II-A, III-B, IV-C, V-D, VI-E, VII-F#. So we see that "D" is a fifth interval from "G" and we place it on the circle. If we continue to do this the complete circle will follow...

C - G - D - A - E - B - C#/Bb - F#/Gb - Db - Ab - Eb - Bb - F - C

This is in fifths but if we turn it around and reverse the direction of the circle we are looking at fourths...

C - F - Bb - Eb - Ab - Db - Gb/F# - Bb/C# - B - E - A - D - G - C

The guitar is tuned in fourths so this is an excellent way to instantly identify the notes on the guitar. Notice the spelling of BEAD and hence the name BEAD Method

It's also a great way to know what chords play together. They are grouped in threes. If you play the minor of each chord you will have a full complement of chords.

Hope that helps,

Manx