Music intervals explained
Slide the upper note away from the lower one, half step by half step, and hear each interval’s character.
perfect 5th
C4 → G4 · 7 half steps · P5
Hollow and strong — the "Star Wars" leap.
Frequency ratio in equal temperament: 1.498 — close to the simple ratio 3:2, which is why it sounds so stable.
Why intervals sound the way they do
When two notes’ frequencies form a simple ratio, their vibrations line up often and the ear hears them as blending — consonant. An octave is exactly 2:1, a perfect 5th almost exactly 3:2, a major 3rd close to 5:4. The minor 2nd and tritone have no simple ratio, and the waves beat against each other, which we hear as tension.
Modern pianos use equal temperament: every half step multiplies the frequency by the twelfth root of 2 (about 1.0595). This slightly bends the pure ratios, but it means every key sounds equally in tune — the compromise that lets you play in all 12 keys on one instrument.
All intervals within an octave
| Half steps | Interval | From C | Song cue |
|---|---|---|---|
| 0 | C → C | — | |
| 1 | C → D♭ | Jaws theme | |
| 2 | C → D | Happy Birthday | |
| 3 | C → E♭ | Greensleeves | |
| 4 | C → E | When the Saints Go Marching In | |
| 5 | C → F | Here Comes the Bride | |
| 6 | C → G♭ | The Simpsons theme | |
| 7 | C → G | Star Wars main theme | |
| 8 | C → A♭ | The Entertainer (E up to C) | |
| 9 | C → A | My Bonnie | |
| 10 | C → B♭ | Somewhere (West Side Story) | |
| 11 | C → B | Take On Me (chorus leap) | |
| 12 | C → C | Somewhere Over the Rainbow |
Ready to test yourself? Try interval ear training.
Questions
What is an interval in music?
The distance between two notes, measured in half steps (adjacent keys on a piano). C to E is four half steps — a major 3rd. Intervals are the building blocks of melodies (notes one after another) and chords (notes together).
What does “perfect” mean for an interval?
Unisons, 4ths, 5ths and octaves are called perfect because they appear unchanged in both the major and minor scales and have very simple frequency ratios (a 5th is about 3:2, an octave exactly 2:1). 2nds, 3rds, 6ths and 7ths come in major and minor versions.
How can I learn to recognise intervals by ear?
Link each interval to the opening of a song you know — a perfect 4th is “Here Comes the Bride”, a perfect 5th is the Star Wars theme — then drill with random examples. The interval ear-training exercise on PianoForge does exactly this.
What is a tritone?
An interval of six half steps — exactly half an octave — also called an augmented 4th or diminished 5th. It sounds unstable, which is why the tritone inside a dominant 7th chord pulls so strongly to resolve.