Guitar Music Theory

Guitar music theory is an important part of understanding what your playing and figuring out what somebody else is playing.

At a very basic level, this may involve knowing what chords fit within a given key, for example, knowing that the following chords all fit within the key of G Major: G, Amin, Bmin, C, D, Emin, and F#dim. So, once you determine a given piece of music is in the key of G Major, it’s a good bet several of the above chords will show up somewhere in the piece.

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From a rock lead perspective, you’ll get a lot of mileage out of knowing how pentatonic scales relate to a given key. The number of solos that have been written using the E Pentatonic Minor scale in the 12th position alone is a bit mind boggling.

However, theory can come in handy in significantly more sophisticated ways. As an intermediate example, I used to have a guitar teacher that would have me practice various intervals within a given key (i.e. playing them “diatonically”). For the sixth intervals, I would play them on the G string as follows (this is in the Key of A Major):

One time I was transcribing the song Just What I Needed by The Cars. Pretty easily, I was able to determine the song’s in the key of E Major (the song starting with a bunch of E chords was a big clue). The chords for the rhythm guitar were taken straight from the major and minor chords of the Key, the main verse was a I-V-vi-ii chord progression (if you don’t know what that means, don’t worry). The verse variations and the chorus were equally as easy to figure out.

The interesting part was the guitar solo. The solo was mostly based on the E Pentatonic Major scale using the familiar pentatonic pattern at the 9th fret.

However, at the end of the guitar solo, I could hear that Elliot Easton was ascending up the neck in some fashion that was not pentatonic. Once I established that the initial interval was a sixth (which I did using Transcribe! - see our Transcribe! Review), I quickly figured out that he was ascending from the root to the fifth on the G string using sixths with a chromatic sixth thrown in at the flat fifth. Specifically, the lick was (again, this is the Key of E Major):

Without an understanding of sixths and how they relate to the parent key, this would have been a pain to figure out. With that understanding, it was easy.

My advice to you? Do yourself a favor. Invest some time, effort and money. Get some quality instruction and develop a solid foundation in guitar music theory. It will help with all aspects of your playing.

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