What an interval is
Interval is the distance between two notes. Its name has two parts:
- O number (2nd, 3rd, 5th…): how many letters you count, including the first and the last. From C to E: C, D, E = 3 letters = third.
- A quality (major, minor, perfect, augmented, diminished): the exact size, in half steps.
The interval chart
| Interval | Half steps | Starting from C | Symbol |
|---|---|---|---|
| Unison | 0 | C | 1 |
| Minor second | 1 | D♭ | ♭2 |
| Major second | 2 | D | 2 |
| Minor third | 3 | E♭ | ♭3 |
| Major third | 4 | E | 3 |
| Perfect fourth | 5 | F | 4 |
| Augmented fourth / diminished fifth (tritone) | 6 | F♯ / G♭ | ♯4 / ♭5 |
| Perfect fifth | 7 | G | 5 |
| Augmented fifth | 8 | G♯ | ♯5 |
| Minor sixth | 8 | A♭ | ♭6 |
| Major sixth | 9 | A | 6 |
| Minor seventh | 10 | B♭ | ♭7 |
| Major seventh | 11 | B | 7 |
| Perfect octave | 12 | C (high) | 8 |
Major third and minor third: the heart of chords
The third decides whether a chord is major or minor:
C → E: bright, “happy” sound.
C → E♭: darker, “sad” sound.
Learn by playing. In Dedilhado Vivo you see where each finger presses, play for real and the app checks you through the microphone. Free, no sign-up.
Open the free app →Perfect fifth: the solid foundation
A perfect fifth (7 half steps) is the most stable interval after the octave. It's in almost every chord and is the basis of the power chord of rock.
Major seventh and minor seventh
A seventh is the note that turns a triad into a seventh chord. It has two very common versions:
C → B♭. It's the seventh of C7 and Cm7.
C → B. It's the seventh of C7M.
An easy way to find it: the minor seventh is a whole step down of the octave; the major seventh, a half step down. This is explained hands-on in seventh chords.
Octave: the same note, higher
A octave has 12 half steps and connects two notes with the same name. It sounds so “alike” because the frequency of the upper note is exactly twice of the one below. See more in octave, ninth and extensions.
Why are some “perfect”?
Unison, fourth, fifth and octave are called perfect because they have only one “natural” size in the major scale and sound very stable. If they get a half step bigger, they become augmented; a half step smaller, diminished. The others (2nd, 3rd, 6th and 7th) are major or minor.
The tritone: the interval of tension
At 6 half steps, the tritone splits the octave exactly in half. It sounds unstable and “asks” to resolve. It's what gives the dominant seventh chord its strength (G7 has B and F, a tritone), which pulls toward C.
Songs to recognize intervals by ear
| Interval | Song opening (going up) |
|---|---|
| Major second | Happy Birthday (from “hap-py” to “birth”) |
| Major third | “When the saints go marching in” (“Oh, when”) |
| Perfect fourth | Wedding March (“Here Comes the Bride”) |
| Perfect fifth | Twinkle, Twinkle, Little Star (“Twin-kle, twin-kle”, from the 1st to the 2nd “twinkle”) |
| Major sixth | “My Bonnie lies over the ocean” (“My Bon-”) |
| Octave | “Somewhere over the rainbow” (“Some-where”) |
Interval inversion
If you invert an interval (the bottom note goes on top), the numbers add up to 9 and the quality flips: major ↔ minor, augmented ↔ diminished, perfect stays perfect. Example: C→E is a major third; E→C (the C above) is a minor sixth. 3 + 6 = 9.
Now put the theory into your fingers
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Practice theory in the free appFrequently asked questions
How many half steps are in a major third?
Four. A minor third has three.
What's the difference between a major seventh and a minor seventh?
The major seventh is 11 half steps (a half step below the octave). The minor seventh is 10 half steps (a whole step below the octave). From C: B is the major seventh and B♭ is the minor seventh.
What is a perfect interval?
Unison, fourth, fifth and octave, the most stable intervals. They aren't called major or minor, but perfect, augmented or diminished.
What is a tritone?
An interval of three whole steps (6 half steps), like F–B. It's unstable and creates the tension of the dominant seventh chord.