Intervals

An interval is the distance between two things.
In the case of music, an interval is the distance between two notes.

Musical intervals are measured in terms of size and quality.

Interval Size

The size of an interval is an Arabic numeral that indicates the number of notes between the two notes.

To get the size, start on one note, counting it as 1, and count each line or space/note name until you reach the second note. (Count inclusively.) The number of the second note will be the size of the interval.

An example of how to count a third is below:

The size of the interval is like the scale degree number In the example above, think about F-A in the key of F. A is then scale degree 3. F-A is an interval of a third.

An example of counting an interval the size of a fourth is below:

Simple and compound intervals

Intervals that have a size of 1 through 8 are called simple intervals; they are intervals contained within an octave.

Intervals that are of a size larger than an octave (e.g., 9, 11, 1) are compound intervals. More on these in another lesson.

Interval quality

Intervals can be Major, minor, Perfect, diminished or augmented in quality.

Let’s start with the intervals contained in a major scale:.

Here is the major scale:

Major and perfect intervals

Below are the intervals from the first note of the major scale to each other note:

There are two types of interval qualities in the major scale: Major (M) and Perfect (P).

Intervals that are of size 1, 4, 5, 8 are Perfect (P).

The numbers under the intervals above refer to the scale degrees in C – the key of the first note. For example, in the second interval above, the two notes, C-F, are scale degrees 1 and 4 of the C major scale.

Therefore, the Perfect intervals can be thought of as scale degrees:
P1 = scale degrees 1-1
P4 = scale degrees 1-4
P5 = scale degrees 1-5
P8 = scale degrees 1-8

Intervals of size 2, 3, 6, 7 are Major (M).

Major intervals as scale degrees:
Major 2 = scale degrees 1-2
Major 3 = scale degrees 1-3
Major 6 = scale degrees 1-6
Major 7 = scale degrees 1-7

Major and Perfect intervals also can be thought of this way: If the top note of the interval fits in the major scale that starts on the bottom note, they are the major or perfect intervals (based on size).

If either note is changed from the note that is in the major scale – making the interval larger or smaller — then the quality changes.

Making intervals larger

You can make an interval larger by lowering the bottom note or raising the top note:

When writing intervals, never change the given note.

Making intervals smaller

You can make an interval smaller by lowering the top note or raising the bottom note.

When notating intervals, never change the given note.

Augmented intervals

Making a Perfect or Major interval one-half step larger will create an Augmented interval. Leaving the bottom note alone,

In scale degrees:

Aug 1 = 1-#1
Aug 2 = 1 #2
Aug 3 = 1-#3
Aug 4 = 1-#4
Aug 5 = 1-#5
Aug 6 = 1-#6
Aug 7 = 1-#7
Aug 8 = 1-#8

Minor intervals

Only intervals that were major can be minor in quality.
Intervals that are Perfect (1, 4, 5, 8) CANNOT be minor.

Making a Major interval one half-step smaller makes it minor (m) in quality.

In scale degrees:
minor 2 = 1-b2
minor 3 = 1-b3
minor 6 = 1-b6
minor 7 = 1-b7

Diminished intervals

Making either a minor interval or a Perfect interval one half-step smaller creates a diminished (d) interval:

In scale degrees:
dim 1 = n/a
dim 4 = 1-b4
dim 5 = 1-b5
dim 8 = 1-b8

dim 2 = 1-bb2
dim 3 = 1-bb3
dim 6 = 1-bb6
dim 7 = 1-bb7

Note that a diminished 1 (diminished unison) does not exist. You cannot make a unison smaller. Lowering the second note of a P1 makes the interval larger, making it an A1.

Summary

Intervals that are 1, 4, 5, 8 in size can be perfect, augmented, or diminished.
Intervals that are 2, 3, 6, 7 in size can be Major, minor, augmented, or diminished.

The qualities can be visualized as in the following chart: