What Is an Interval in Music?
An interval is just the distance between two notes. That's it. But it's also the basic unit every melody and chord you've ever heard is built from, and once you learn the names, everything in ear training gets easier to talk about, practice, and hear.
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The definition, without the jargon
Play any two notes and you've made an interval. We measure its size in semitones (also called half steps): the distance from one piano key to its immediate neighbor, black keys included, or one fret on a guitar. Two semitones make a whole step. And that's honestly the whole measuring system. Every interval name below is just a label for a particular number of semitones.
When the two notes come one after the other, the interval is melodic: that's what melodies are made of. When they sound at the same time, it's harmonic: the stuff of harmony and chords. The distance is exactly the same either way; only the presentation changes. Your ear needs practice with both.
All 13 intervals within an octave
Here's the complete set, from two identical notes (unison) up to the same note eight letter-names higher (octave), each with an example starting from C:
| Interval | Semitones | Example from C | Character |
|---|---|---|---|
| Unison | 0 | C → C | Same note |
| Minor 2nd | 1 | C → D♠| Tense, crunchy |
| Major 2nd | 2 | C → D | A plain step |
| Minor 3rd | 3 | C → E♠| Dark, sad |
| Major 3rd | 4 | C → E | Bright, happy |
| Perfect 4th | 5 | C → F | Open, sturdy |
| Tritone | 6 | C → F♯ | Unstable, eerie |
| Perfect 5th | 7 | C → G | Strong, hollow |
| Minor 6th | 8 | C → A♠| Bittersweet |
| Major 6th | 9 | C → A | Warm, singing |
| Minor 7th | 10 | C → B♠| Restless, bluesy |
| Major 7th | 11 | C → B | Sharp, yearning |
| Octave | 12 | C → C | Same note, higher |
Take that "character" column as a starting hint, not a rule. Context and register change how an interval feels. Still, those little impressions are close to how most listeners describe each sound, and they give your ear something to hold onto while it's learning.
How the naming system works
The number in an interval's name counts letter names, and it counts both ends: C up to E spans C, D, E (three letters), so it's a 3rd. The quality word narrows things down from there:
- Perfect covers unisons, 4ths, 5ths, and octaves. Their sound waves line up in the simplest ratios (an octave is exactly 2:1, a fifth about 3:2), which is why they sound so stable, and why they picked up the flattering name centuries ago.
- Major and minor cover 2nds, 3rds, 6ths, and 7ths. Each comes in two sizes a semitone apart: the larger one is major, the smaller minor. And that minor 3rd versus major 3rd difference is the very thing that makes minor chords sound sad and major chords sound bright.
- The tritone (6 semitones) sits alone in the middle. Technically it's an augmented 4th or a diminished 5th, but everyone just calls it the tritone. It's the most unstable interval we have, the engine of tension in dominant chords.
Consonance and dissonance
Every interval sits somewhere on a spectrum from restful to tense. Consonant intervals (octaves, 5ths, 4ths, 3rds, and 6ths) sound settled; they can sit still. Dissonant intervals (2nds, 7ths, and the tritone) sound like they need to go somewhere, and music leans on that pull to create motion. Neither one is better. A piece with no dissonance at all is wallpaper. And for ear training, the split is actually a gift: the dissonant intervals are often the easiest to recognize, because they sting.
How to learn to hear each interval
- Start with four: minor 2nd, major 2nd, perfect 4th, perfect 5th. They sound about as different from each other as intervals can.
- Attach an anchor song to each one. "Happy Birthday" opens with a major 2nd; the Star Wars theme leaps a perfect 5th. Our anchor songs list covers every interval, ascending and descending.
- Sing every interval you hear before you answer. Singing is the difference between recognizing a sound and actually knowing it.
- Drill short daily sessions in the interval trainer. It plays real instrument sounds and asks you what you heard, first by name, then by the actual pitches.
- Add the rest in contrasting pairs (minor 3rd with major 6th, say), and always compare a new sound against one you already own.
Want the full route through notes, intervals, and chords from scratch? That's our guide to ear training. And when you're ready for stacked intervals, move on to recognizing chords by ear.
Frequently asked questions
What is an interval in music?
The distance in pitch between two notes, measured in semitones. Play them one after the other and it's a melodic interval; play them together and it's a harmonic one. Every melody and every chord you know is built from them.
How many intervals are there in an octave?
Thirteen, counting both ends from the unison (0 semitones) up to the octave (12 semitones): unison, minor and major 2nd, minor and major 3rd, perfect 4th, tritone, perfect 5th, minor and major 6th, minor and major 7th, and the octave.
Why are some intervals called perfect?
Because unisons, 4ths, 5ths, and octaves vibrate in the simplest ratios and sound the most stable, early theorists singled them out for it. Each comes in just one flavor, while 2nds, 3rds, 6ths, and 7ths each have a major and a minor version a semitone apart.
Which intervals should I learn first?
Start with the minor 2nd, major 2nd, perfect 4th, and perfect 5th: four sounds that are genuinely easy to tell apart. Once those feel reliable, add the others in pairs, comparing each new interval against one you already know.