An interval is simply the distance between 2 notes, in steps. An interval can be as small as a half step or as large as several octaves. The best thing to remember when counting intervals in music is that you always count the note you’re on. For instance, within the C major scale there are intervals between the tonic (C), and every other note in the scale.
C major scale
1 2 3 4 5 6 7 8
C D E F G A B C
We say that the 3rd of C is E. All we need to do is count to 3. Note, however, that we are counting C as ‘one’. So, in essence, 1+3=3, unlike mathematics, where 1+3=4. Keeping this in mind, the 2nd of C is D, the 6th of C is A, and so on. As you progress, you will find all intervals have a specific name, depending on the specific distance between them. As with sharp and flat notes, there are always 2 names for each of these intervals. The terms diminished and augmented, or major and minor, are used to label these intervals.
Begin by understanding this:
1. The distance of 1whole step (2 frets) is called a major second
Example: C to D
2. The distance of 2 whole steps is called a major third.
Example: C to E
3. The distance of 1 ½ steps is called a minor third
C to Eb
4. The distance of 2 ½ steps is called a perfect fourth
Example C to F
5. The distance of 31/2 steps is called a perfect fifth
Example: C to G
Note that the 4th and 5th are called ‘perfect’. No other intervals in the scale are perfect, only the 4th and 5th. This is because of their very high degree of consonance. The term consonance simply means notes that sound harmonious together, restful, without tension. Dissonance is the opposite of this. An example of a dissonant interval is the diminished fifth (3 whole steps), known as the tritone. Example C to Gb
Learning the intervals of the major scale trains the ear and helps you to hear music more intuitively. Compare the sounds of various intervals here:
http://sourceforge.net/projects/tete/
©2012Jim Greenfield