Understanding Intervals

1. What is an Interval?

In music theory, an interval is simply the distance in pitch between two notes. If you play the two notes together at the same time, it is called a harmonic interval. If you play them one after the other, it is called a melodic interval.

(Example: A Perfect 5th, C to G)

2. The Two Parts of a Name

Every interval has a precise two-part name. The name tells you exactly how far apart the notes are, both in written lines/spaces on a staff, and in exact piano keys (semitones).

• The Number (Size): 2nd, 3rd, 4th, 5th, etc. This is found simply by counting letter names.
• The Quality: Major, Minor, Perfect, Augmented, or Diminished. This tells you the exact number of semitones.

Step 1: Finding the Number

To find the number, simply count the letter names from the bottom note to the top note, including both the start and end notes.

3. Understanding Qualities & Hearing Them

Once you have the number, you apply a Quality. The easiest way to learn qualities is to use the Major Scale of the bottom note. If the top note belongs to the major scale of the bottom note, the interval is either Major (for 2nds, 3rds, 6ths, 7ths) or Perfect (for Unisons, 4ths, 5ths, Octaves).

The "Perfect" Intervals (1, 4, 5, 8)

Named "perfect" because of their highly consonant, stable sound ratios in physics.

Major & Minor Intervals (2, 3, 6, 7)

If you take a Major interval and flatten the top note by one semitone, it becomes Minor. Minor intervals sound darker, while Major intervals sound brighter.

Augmented & Diminished (The Dissonants)

If a Perfect or Major interval is made larger by a semitone, it becomes Augmented.
If a Perfect or Minor interval is made smaller by a semitone, it becomes Diminished.

4. Summary Cheat Sheet