Introduction to Intervals, Interval Size

Interval is the difference between any two pitches. There are two key parts to describing this difference, size and quality. Interval size is a count of the total number of notes covered from one pitch to the other. For example, the pitches A to D involves a span of four notes, starting on A and skipping over B and C to reach D. If we count the total number of letters involved we get four, A-B-C-D, therefore the size of the interval is referred to as a fourth.

Interval quality is a description of the total number of whole and half steps between two pitches. Interval quality is a more complicated and nuanced topic, so it will be covered in subsequent lessons following this introduction and lesson on interval size. 

We will focus our interval lessons on simple intervals. Simple intervals are the eight intervals from unison/prime (1) to the octave (8). Here is a table of the simple intervals that includes the number used for their size, the way we speak the interval size, the letter names of the notes, and an example interval:

Size Spoken Example Letters Notation
1 Unison or Prime A - A
2 Second A - B
3 Third A - C
4 Fourth A - D
5 Fifth A - E
6 Sixth A - F
7 Seventh A - G
8 Octave A - A

There are two ways intervals are presented in notation:

  • Melodic intervals happen one note after another (also called linear intervals)
  • Harmonic interval happen simultaneously (also called vertical intervals)

Here is an example of a third as a melodic interval and a third as a harmonic interval:

The distinction between a melodic and harmonic interval is only to show how me might encounter intervals in music notation. In both instances, the size and quality of the interval are exactly the same.

Again, interval size is determined by the total span of notes from one note to another. This includes counting the starting and ending letters, and any letters that fall in-between. The other way to approach this is to count the total lines and spaces spanning the two notes, including the lines or spaces of the starting and ending notes. The examples below show both of these processes adding up to the interval size of a fifth.  

Let's get some practice counting interval size. If you are counting letters, count all letters from the bottom note to top note. If you are counting lines and spaces, count all lines and spaces from the bottom note to the top note. For each of these examples, do your best to find the size, then click the answer button to check your solution.