Major Scale
Note: Please read article post Understanding Scale Modes to help prepare for Pentatonic Scale Inside The Major Scale On Guitar
This article post is about the scale myth and confusion of how the Pentatonic Scale relates to the Major Scale. The biggest confusion is what key am I really playing in when I am working with two types of scales (Major Scale Versus Pentatonic Scales) and how do they interact and relate to each other? In a live improvisation playing situations where your not sure of what key your playing in. The first thing your usually going to do by ear is find that common Minor Pentatonic Scale Box and see what chord changes are being played. You usually are not going to try playing any major scale 1/2 step notes until you are absolutely sure what major scale key your playing in.
If your playing with Blues and Rock Players unto Jazz and Classical Players. The scale key that is called out may be very different unto the class and school of musicians that your playing with. Jazz and Classical players are usually more schooled in music theory and they relate the key to the key signature of the Major Scale. A lot of Jazz players are more concerned with modes and the tonal center. Blues and Rock players on the other hand relate the key to the Minor Pentatonic Scale (The bordered notes shown in the fingering on the first row). Blues players usually stay in Pentatonic and Blues Scales (Major scales are a taboo). The I of the I , IV, V chord progression dictates were the Minor Pentatonic Key lies and that is how they relate the key. Rock players use both but more in the pentatonic and blues scales.
Here is the big kicker, three different Pentatonic Scale Keys can be super imposed on the major scale. The Minor Pentatonic Scale can be super imposed on the three minor modes of the major scale – (vi) Aeolian Scale or Natural Minor Scale, (ii) Dorian Scale, (iii) Phrygian Scale (1st row of the fingering diagrams). The chord progression order of the chords being played is what’s going to rule this relationship. The (G Major Triad Chord Scale Chart) shown below shows the major chord scale order and what relates to the scale fingerings below.
The (Diagram – Fret 5 A Dorian Scale/ A Minor Pentatonic Scale) is the most common relationship found and it’s usually when the IV chord is Major. This one is common in a lot of I, IV, V. Blues & Rock Progressions. The next commonly found relationship is the Aeolian Scale/ Minor Pentatonic Scale. This usually is when the IV chord is minor.
The least common relationship is the (Diagram- Fret 7 B Phrygian Scale / B Minor Pentatonic Scale). This can happen if the II Chord is Major. The simplest overview of all of this technical jargon is to analyze the chords that are being played within the Minor Pentatonic Scale fingering. This gives you a clue to the notes of the major scale mode and what major scale key your playing in.
If a guitar player with a good ear has practiced both types of scales, they can usually find their way around both scales relationships easier. You can never stop getting better at scales. The more you practice and apply yourself to play each of these scale relationships in your solos. The better your is ear is going to become in adapting playing to different types of chord progressions. Guitar Analyzer Software can instantly display how the three pentatonic scales can fit inside every major scale key as shown below.
G Major Triad Chord Scale Chart
The guitar scales fret-board diagrams shown below display the D Dorian Scale Mode. The Dorian Scale Mode is the 2nd degree of the Major Scale (Ionian Mode). In playing scales on guitar the big confusion of understanding major scale modes is that people think your playing in another scale. It is the same scale of the major scale but your start note is the second note of the major scale and ends in the second note of the next octave. The D Dorian for example is still the C Major Scale. The root note is outlined by the note in the square of the guitar scales fretboard diagrams.
The scale formula of the Dorian Scale is (1, 2, b3, 4, 5, 6, b7). The minor 3rd (b3) of the scale makes it a minor sounding scale. The only difference between Dorian Scale and The Natural Minor Scale (Aeolian Mode) is the raised Major 6 (6th) from a Minor 6 (b6).
The Dorian Scale has unique tonal personality which reminds me of the background music in a western movie like a cowboy riding off in the sunset. The guitar fret-board fingering diagrams below show the intervals, notes, and finger placement for 2 octave fingerings. Practice these fingering and carefully listen to the sound while you play the notes and really hear what the Dorian Scale sounds like. Related Post > Understand Major Scale Modes
Guitar Scale Interval Theory Application
All chromatic guitar scale intervals spaced fret by fret on the guitar have 12 half steps. These are finite parts that make up all scales. Music intervals are like a measurement ruler to measure the distance between notes. We measure the distance between notes in half steps instead of inches like a ruler (Ex.1).
Ex.1) 
Instead of 1-12 it’s 1-7 and we have 5 accidental numbers b2, b3, b5, b6, b7 none between 3&4, 7&1 (Ex.2).
Ex.2) 
In music scale theory numbers are used for intervals as an easier way to measure the distance of steps between notes in a music scale or chord. If we count higher than 7 we go into the next octave and 1 starts over again as the 1 in the square of this chromatic scale on the guitar scale fret board (Ex.1). This applies to music scale theory and playing scales on guitar. In chord theory harmony we use interval numbers higher than (7) called compound intervals this will be explained later in future lesson.
Every music scale has scale formula (1, 2, 3, 4, 5, 6, 7 is the Major Scale Ex.4), (1, b3, 4, b6, b7 is the Minor 6 Pentatonic Scale Ex. 5) the bordered numbers. The notes in music are taken from the first 7 letters of the alphabet A-G with 5 accidentals that each have with 2 names (increment A to A# sharps & decrement B to Bb flats) C#-Db, D#-Eb, F#-Gb, G#-Ab. There is no accidental notes between B-C, and E-F (Ex.3). This can be a challenge to learn from our old mental habits of how we use letters in the alphabet also as numbers in counting.
The Guitar Analyzer Diagrams below display visually how to understand intervals. Showing dynamically how the scale formula bordered notes overlay the measuring distance between the notes. This creates an easy way visualize guitar scale shapes to aid guitar players who play by ear.
Ex.1 
Ex.3 
Ex.4 
Ex.5 