In music, an **interval** is the distance between two pitches, expressed either simultaneously (**harmonic interval**) or in succession (**melodic interval**). In **Example 1** below, the first interval is harmonic because the notes F and D occur at the same time whereas the second interval is melodic because the note D occurs after F. **Example 1.** Harmonic vs. melodic intervals. ![[intervals example 1.png]] ## Interval Size The size of an interval corresponds to the number of lines and spaces (or letter names) that it spans. When counting the number of lines and spaces between the notes of an interval, we include the first note in the count, starting at 1. Interval sizes are named using ordinal numbers (e.g. second, third, fourth, and so on) except for the **unison** (1) and the **octave** (8). **Example 2** below shows the names and numerical abbreviations for the intervals of the C [[major scale]]. **Example 2.** Interval size with names and numerical abbreviations. ![[intervals example 2.png]] When determining the size of an interval, we ignore any accidentals. As shown in **Example 3** below, F–A♭, F–A♮, and F–A♯ are all considered thirds. **Example 3.** Three thirds with different accidentals. ![[intervals example 3.png]] ## Common Intervals ![[intervals example common intervals.png]] Interval Identification Practice - [[Exercises on musictheory.net]]