Pentatonic scale patterns are easier to use and apply than major scales. In order to apply major scales properly you must examine a whole chord progression and determine which key all the chords fit into together. But when applying the pentatonic scale, you only need to identify the root chord in the progression and then play a pentatonic key that corresponds to it. Below I’ll explain why you can play the pentatonic based off only the root of a song and not the whole key or parent major scale.
The pentatonic scale can follow the root chord (which is the chord functioning as the tonal center of a song) because it includes scale degrees common to all possible major scale modes. For example, let’s say you have a progression revolving around a C major chord. Well, the C could be the first chord in the C major scale (Ionian mode), the fourth chord in the G major scale (Lydian mode) or the fifth chord in the F major scale (Mixolydian mode). Each of these modes stem from different major scale keys, but they all include the notes of the C major pentatonic. Below I help point this out by spelling out each major scale and putting the pentatonic notes in bold.
C D E F G A B – C Ionian (C is chord I in the key of C)
C D E F# G A B – C Lydian (C is chord IV in the key of G)
C D E F G A Bb – C Mixolydian (C is chord V in the key of F)
C D E G A – C major pentatonic
The same thing happens in minor keys. If you’re playing a chord progression that revolves around an A minor then the three possible major scale modes are Dorian, Phrygian and Aeolian.
A B C D E F# G – A Dorian (Am is chord ii in the key of G)
A Bb C D E F G – A Phrygian (Am is chord iii in the key of F)
A B C D E F G – A Aeolian (Am is chord vi in the key of C)
A C D E G – A minor pentatonic
You can see that the pentatonic scale is missing the intervals that complete any of the whole major scales (these same missing scale degrees are what make each mode sound different). Without them there is no conflict regardless of mode. In fact, if a chord progression changes keys (parent major scale/mode) but still revolves around the same chord, then you can still play the same pentatonic scale over it without needing to change keys. For example, “Moondance” by Van Morrison has a section based on A Dorian and another section based on A Aeolian. If you want to play full major scale patterns then you’ll need to switch keys. But since both sections revolve around the same Am chord you can continue to play A minor pentatonic scale patterns over both modes.
Pentatonic scale patterns are easier to apply and require less thought or guitar theory knowledge for the reasons explained above. Because the pentatonic is simpler in this regard, some guitar players consider it less technical or less sophisticated, but I don’t think that way. Often times the simple sound of the pentatonic scale is a better choice.
To learn more about music theory for guitar, including scales, chords, progressions, modes, and more, sign up for a free preview of my Fretboard Theory books and DVDs by using the form on this web page.
Play Until Yer Fingers Bleed!
Mr. Desi Serna