What is an interval? To put it simply, it is the distance between 2 notes. These distances are the building blocks of all scales and chords.
How intervals relate to each other in a chord or scale can also actually affect its “mood”. Minor chords and scales “feel” different than major chords and scales. Anything minor has a “sadder” sound that anything “major”.
Now, earlier, I used the phrase “to put is simply”. But interval theory is really a complicated subject. Because this is an article for beginning students, I’m going to try to simplify this for now.
There are two things that make up an interval — the “number”, and the “quality”. An interval number is the distance between any two letter names (ABCDEFGA). The quality of an interval involves a lot of complicated definitions.
The “number” part of an interval is the numeric distance from one note to another: I’m only starting from the letter A because it is the first letter of the musical alphabet. I could start from any letter.
A B C D E F G A
1 2 3 4 5 6 7 8
Looking at this:
B is the 2nd of A
C is the 3rd of A
D is the 4th of A
E is the 5th of A
F is the 6th of A
G is the 7th of A
A is the octave (8) of A
Not only that, but
C is not only the 3rd of A, but also the 2nd of B. (B C D E F G A B)
E is not only the 5th of A, but also the 3rd of C (C D E F G A B C)
G is not only the 7th of A, but also the 5th of of C (C D E F G A B C)
This whole thing begins to get messy when you start talking about the “quality” of an interval. The quality of an interval has to do with the number of 1/2 steps it takes to get from the first letter to the second letter.
Let’s use the Chromatic Scale to show this:
A A#/Bb B C C#/Db D D#/Eb E F F#/Gb G G#/Ab A
The Chromatic Scale is also called a 1/2 step scale because the distance between each note is 1/2 step. It also defines all of the notes in music.
A piano IS a chromatic scale. The white keys are a continuous “diatonic scale” (ABCDEFGABC…). Once you add the black keys, which are the sharps and flats, you have the Chromatic Scale. Here’s how we are going to use it:
C D E F G A B C
E is the 3rd of C
G is the 3rd of E (E F G A B C D E)
But look at these two numeric intervals for a moment. If you look at the Chromatic Scale you will see that the number of 1/2 steps between C and E is 4, and the number of 1/2 steps between E and G is 3. But they are BOTH considered to be 3rds!
This is where the quality of these 3rds come in. The 4 “1/2 step” 3rd is called a “major 3rd”, and the 3 “1/2 step” 3rd is called a minor 3rd. So C to E is a major 3rd, and E to G is a minor 3rd.
In general, when we talk about intervals, we use the letter name including any sharp or flat that it may contain, to get the “number” value. We use the Chromatic Scale to get the “quality”.
For example, an E chord is made up of the following notes:
E G# B
G# is the 3rd of E (E F G…)
B is the 3rd of G# (G A B)
Now if we add the sharp (#) to the G and look at the Chromatic scale, we find that:
E to G# is a major 3rd (4 “1/2” steps)
G# to B is a minor 3rd (3 “1/2” steps)
Now all of this hullabaloo was just for the “3rd”. The other numeric values have their own qualities. I don’t want to get into all of that here in this article.
What you should get out of this at this point is that:
1. Intervals are the building blocks of scales and chords
2. Intervals have both a numeric value and a quality value.
As time goes on, you will learn more and more about intervals. This is just to get you started.