Perfect fourth: hear it in Here Comes the Bride
The perfect fourth is 5 semitones. Play it, recognise it from Here Comes the Bride and Amazing Grace, and tell it from the fifth.
A perfect fourth is 5 semitones, such as C up to F. It sounds open and expectant, like a call to attention: the rising fourth starts Here Comes the Bride and Amazing Grace. Turned upside down it becomes a perfect fifth.
Listen to a perfect fourth
C to F: 5 semitones.
What does a perfect fourth sound like?
Open and hollow like the fifth, but less settled: a rising fourth feels like it is announcing something. Harmonically it is consonant yet slightly unresolved.
Songs that start with a perfect fourth
| Song | Direction | Where |
|---|---|---|
| Here Comes the Bride (Bridal Chorus, Wagner) | Up | the first two notes |
| Amazing Grace | Up | the first two notes |
| Auld Lang Syne | Up | the first two notes |
| Eine kleine Nachtmusik (Mozart) | Down | the first two notes |
Titles only. Each melody's opening was checked note by note; songs we were not sure of are left out.
How do you recognise a perfect fourth by ear?
- Hum the first two notes of Here Comes the Bride: that leap is the fourth.
- Fourth or fifth? Both sound open. The fourth is smaller (5 semitones vs 7) and often feels like it lands "home" on the top note; the fifth feels like it lands home on the bottom note.
- Sol up to do (the dominant up to the tonic) is a perfect fourth: many melodies start that way.
Quick test: perfect fourth or not?
Four sounds. Each one is a perfect fourth or one of the intervals people confuse it with. Listen, then pick.
Score: / 4 (your score updates as you answer)
The perfect fourth on every note
Intervals are spelled by letter: a perfect fourth always spans 4 letter names, which is why the top note is sometimes a sharp or a flat.
| From | Perfect fourth up | Hear it |
|---|---|---|
| C | F | |
| D♭ | G♭ | |
| D | G | |
| E♭ | A♭ | |
| E | A | |
| F | B♭ | |
| F♯ | B | |
| G | C | |
| A♭ | D♭ | |
| A | D | |
| B♭ | E♭ | |
| B | E |
Perfect fourth in numbers
| Measure | Value |
|---|---|
| Semitones | 5 |
| Size on a piano (equal temperament) | 500 cents |
| Pure (just) ratio | 4:3 = 498.0 cents |
| Piano vs pure | +2.0 cents |
| Inversion | Perfect fifth (7 semitones) |
Frequently asked questions
How many semitones are in a perfect fourth?
Five. For example C to F, D to G, or E to A.
What is the difference between a perfect fourth and a perfect fifth?
Two semitones. A fourth is 5 semitones, a fifth is 7, and together they make an octave (C up to F is a fourth, F up to the next C is a fifth).
Which perfect fourth is not perfect?
F up to B. It spans four letter names but measures 6 semitones, so it is an augmented fourth (a tritone). Every other fourth between white keys is perfect.
What song starts with a perfect fourth?
Here Comes the Bride, Amazing Grace and Auld Lang Syne start with a rising perfect fourth; Eine kleine Nachtmusik starts with a falling one.