Useful Music Theory Part 1: The Major Scale And Intervals And Getting A Basis For All Future Music Theory

author: UtBDan date: 08/20/2012 category: guitar scales and modes
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Useful Music Theory Part 1: The Major Scale And Intervals And Getting A Basis For All Future Music Theory
Too often, people come up to me asking to learn "advanced music theory". This in itself is not a problem, but I find a lot of people don't even truly have the basics down. People think because they know the fingerings and the box to a major scale, that they understand the major scale.
I'm not here to teach you how to play something. I'm here to teach you to understand what you're playing.
On that, I'll still show you your basic major scale two octave box shape: based on the E string. This is G major:

or, on bass guitar,

(4) marks where & when you should move your index finger on your fretting hand.
So that's how you play it... but what makes it the major scale? As in, why are those notes what they are?
You form the major scale by taking a starting note (the root) and then move up in the following steps: Whole step, Whole step, Half step, Whole step, Whole step, Whole step, Half step. Don't know what steps are? Think of a whole step as two frets or two chromatic notes, and a half step as one fret or one chromatic note.
Thus, C Major is all the white keys on piano, because it is... C, D, E, F, G, A, B, C.
This pattern will always form the major scale as we all know it. To explain why it became the major scale, I'd have to give you 1200 years of music history and explain how the modes evolved over time, so let's not get into "why is it the major scale" just yet. Just know that pattern is the pattern forming the major scale.
Now, how does this relate to intervals?
A perfect interval is an interval that matches up perfectly with the root note mathematically. But even that statement comes across as rocket science. What does this statement truly mean? It sound waves of a "Perfect 5th" play three times for every two times the sound waves of the root plays. A Perfect 4th does the same thing, but with the inverse ratio: it plays twice for every three times the root plays. The octave is the simplest perfect ratio, as the octave plays twice for every time the root plays.
For this reason, these intervals will always sound groovy played against any other single note. The sound waves bond in a way that is pleases the ear. This is why powerchords sound so awesome: they're just a root, a perfect fifth, and a perfect octave. They can go almost anywhere and do almost anything.
Every other note in the major scale, when referred to as an interval, is called a major interval. Hence, the 2nd note in a major scale? a Major 2nd. 3rd? Major 3rd. 6th? Major 6th. 7th? Major 7th. Thus, a major scale, in addition to being Note Whole step whole step half step whole step whole step whole step half step, could also be viewed as: Root Note, Major 2nd, Major 3rd, Perfect 4th, Perfect 5th, Major 6th, Major 7th, Perfect 8th.
From the major scale, we can name all intervals. How you name intervals goes like this. Assume each arrow (<-- or -->) is a half step up or down.

Diminished <--     Perfect     --> Augmented\r\n
Diminished <-- Minor <-- Major --> Augmented

Hence, if you take a perfect fifth, and take it down one step, it is a... diminished 5th. If you take a perfect fifth and move it up a half step, it is an... augmented fifth. If you take a major third and move it a half step down, it is a... minor third. And so forth.
Hence also, this is why even though C# and Db sound the same, they are different things. Let's say you're playing in the key of F#. C# is a perfect 5th! Db is a diminished 6th. You'll almost never see a Db in the key of F#, cause why would you play a diminished 6th when you could play a perfect 5th? There's more to it than this, but that requires chordal knowledge... which requires a firm understanding in intervals, which is what I'm trying to teach.
I feel this alone is what a lot of musicians fail to get a good grasp of. If you have a firm understanding of intervals and naming them, you can understand or learn almost any kind of theory. The problem is, people learn the major scale and not an understanding of intervals, and then begin to bite off more than they can chew.

I'll follow up this lesson with Useful Music Theory, Part 2: Forming Diatonic Chords and Part 3: The Three Minor Scales.
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