The major scale system is an amazing invention. It consists of an 8 note scale using the same notes as the basic scales. The major scales use accidentals (or half note shifts), whereas basic scales use no accidentals (or whole notes shifts). When you add accidentals to a scale, it changes the basic 8 note scales into 8 note major scales. In other words, a major scale can be made out of any basic scale note by applying the correct accidentals. For me it is purely mathematical and requires tremendous learning and concentration skills over many years to remember each pattern in my muscle memory.
Major scales use the same interval pattern. Regardless of the keynote, the major scale starts on the note of your choice. In the major scale, the intervals are always counted in the same pattern. In particular, the whole notes and half notes appear in a consistent pattern between the 3rd and 4th degrees, and the 7th and 8th degrees.
For future purposes a whole note will be represented as a W. A half note will be indicated by an H.
Ex. #1: Below is the major scale interval pattern applied to the G basic scale: G A B C D E F G [basic scale].
W W H ^ W W W H ^ W major scale interval pattern
1 2 3 4 5 6 7 8
G A B C D E #F G G Major scale.
^ Represents: the area where the half interval goes.
When the basic scale of G has the proper accidentals applied to it as in ex.1 above, it becomes the G major scale. This fact applies to every note in the basic scales.
The starting note for a scale is called the keynote. The above scale is G major. As example #1 shows, the intervals always come between the third and fourth notes/degrees, and the 7th and 8th notes/degrees. So, depending on the note you choose as a keynote, the intervals will naturally rotate, but the finger pattern won’t.
For example, if one is considering a G major scale.
The neck of the guitar has at least 12 frets. Starting with the thickest string, called the low E string: when the string is strummed with no frets pushed down than open e note is sounded. Then as each of the 12 successive fret gets pushed down, the next sequential note is sounded, thus forming the chromatic scale. With that thought in mind, it is easy to establish a consistent pattern to play the major scale on the guitar neck. When this pattern is used in the exact same manner, it produces a major scale on every fret of the guitar neck on the low E string; that is, it produces the entire chromatic set of notes in the major, using all of the tones.
You can play 13 scales total if you start with the proper keynote on the low E string; using all 6 strings on the guitar and the exact same finger pattern, you move up [and down] the neck of the guitar from fret to fret [position to position]. The thirteenth scale or keynote is the octave.
E F #F G #G A #A B C #C D #D E [E being the octave] Chromatic scale.
In finality, the term Tetrachord/s: A method of breaking a major scale into 2 groups of 4 pitches. The upper tetrachord and lower. Both the upper and lower tetrachords of any major scale contain the exact same intervals. Meaning the top and bottom tetrachord both use the interval pattern of two whole steps and one half step. Each tetrachord is seeped by a whole note. Or may be indicated by the W W H w W W H interval pattern.
Guitar lesson review by Daniel Lehrman of Guitar Players Center. GPC