As expected, a website with a name like "Music Theory For Guitar" see's many heated guitar related debates and discussions. Discussions such as the following I found on my Facebook page:
"Music theory is music theory, same on any instrument!"
I totally get where this guy is coming from. What a convenient thing it would be to have music theory work the exact same on all instruments. Though it is critical to understand that music theory on guitar does have it's differences, or else you will make the entire learning process a lot harder on yourself.
Have you ever read through a theory book that assumed that you were able to fluently read music notation? Or play and identify chords/harmonies on a keyboard? The reason for this stems from the fact that books were originally written for institutions such as the Royal Conservatory. In these institutions, students are expected to have a basic set of piano skills, whether piano is their main instrument or not.
These original theory books are now getting copied into newer versions, which is what can leave some guitar players scratching their heads if they don't realize this.
Let us for a moment just think about the guitar and how it is fundamentally different from any other instrument.
First of all, guitars have fretboards where the notes are dispersed in two dimensions. This creates specific patterns for scales/chords etc. that are the same for all keys. For instance, an arpeggio in D major is the same for G major, A major, and so on. It is only the position that you play on the frets that differs.
This is not the same case for instruments such as piano, winds, or brass. Sure, patterns can be found within them to help you play. But they are very different from the patterns that guitarists use.
As for other string instruments (such as cello or violin), I am no expert. But I do know they are tuned in fifths (instead of fourths on the guitar), which changes the patterns they might use.
Not to mention that the modern guitar is not played/used in the same way as any other instrument (more on this later).
All of this is to say that guitar players will understand their instruments differently than a piano player will. There is not one way that is superior than the other, it's just different. Which leads to music theory (hopefully) being taught in different ways.
The guitar can be a lot of things at one given time. It can be melodic, it can be rhythmic and it can be chordal. More often than not, a band will look to the guitar player to improvise their own parts and to just add "cool sounds" over top.
This doesn't only occur in the jam space, but also in the orchestra pit. Take the broadway musical "Hair" for example. The guitarist gets a score that is primarily made up of chord charts. They are then asked to come up with their own rhythms, leads and riffs to play over top of the music. For all 51 musical cues.
Every other instrumentalist will receive a fully notated and detailed score (even the drums). When the keyboardist saw my score I remember them saying "I could never work with that! How is that possible?"
It's possible because I learned the correct music theory for my instrument and know how to quickly play though a chord chart. It actually isn't as hard as it looks!
This isn't to say this is how it goes for all musicals however. Some will still have a notated score for the guitar players as well. For that you will definitely need to work on those sight reading skills.
So depending on what exactly a person hopes to achieve, the study of theory that one focuses on is going to be different for ever person. Even perhaps for two guitar players. Whether you want to improve your sight reading to read scores in a musical, or improve your ear to jam with a band, your theory practice should be different and personalized to fit you.
While music theory should be the same for everyone, in practice, it is not. And if you are learning theory (especially if you are a beginner), it is important to know the difference.
Don't try to learn theory from any old book or online resource you find. Taking the time to find a resource made specifically for guitar, or specifically for what you hope to learn, will greatly help you in the long run. And you might finally see that theory has actually been fun to learn this whole time!
Tommaso Zillio is a professional prog rock/metal guitarist and composer based in Edmonton, AB, Canada.
Tommaso is currently working on an instrumental CD, and an instructional series on fretboard visualization and exotic scales. He is your go-to guy for any and all music theory-related questions.