## Section 5.1 Introduction to Intervals

Intervals are the building blocks of scales, chords (or harmonies), and melodies. Intervals are a measurement between two pitches, either vertically or horizontally. When measuring vertically, we refer to harmonic intervals because the two notes sound simultaneously. When measuring horizontally, we refer to melodic intervals because the notes occur one after the other.

When you measure from the tonic up to each scale degree of a major scale, you find the following intervals:

All intervals in the example above are either “perfect” or “major.”

### Subsection 5.1.1 Numeric Size of Interval

There are two elements to naming intervals: the quality and the number (for example, “major sixth,” abbreviated as “M6”). Let us first focus on the numeric size of intervals.

Odd-numbered intervals will always be a line to a line or a space to a space.

Even-numbered intervals will always be a space to a line or a line to a space.

### Subsection 5.1.2 Interval Quality: Perfect versus Major/Minor

Intervals such as the unison, fourth, fifth, and octave can be classified as “perfect” but never “major” or “minor”. Conversely, the intervals of the second, third, sixth, and seventh can be major or minor but never perfect in quality.

Perfect Intervals: |
Unison, 4th, 5th, 8ve |

Major or Minor Intervals: |
2nd, 3rd, 6th, 7th |

Perfect intervals are always natural to natural, sharp to sharp, and flat to flat except for the fourths and fifths between \(\text{B}\) and \(\text{F}\), which involve \(\text{B}\) to \(\text{F}^♯\) and \(\text{B}^♭\) to \(\text{F}\).

Minor intervals are one half step smaller than major intervals.