Interval · P4 · 5 half steps
The perfect fourth
A perfect fourth is 5 half steps wide, spanning four letter names: C to F. Open, a little unresolved: Here Comes the Bride.
- Half steps5
- Letter names4
- From CC–F
- Inverts toperfect fifth
The perfect fourth on the staff
An interval’s number counts letter names from the bottom note to the top, both included: C, D, E and F is four, a fourth. On the staff, one note is on a line and the other in a space: from a line, it lands in the second space up; from a space, on the second line up.
The number alone doesn’t make it a perfect fourth: perfect means exactly 5 half steps. Check for sharps and flats, including the key signature: C–F is a perfect fourth; move either note by a half step and it changes.
Each example below plays the two notes one after the other (a melodic interval), then together (a harmonic interval).
On the piano
Count half steps: every key, black or white, is one half step from the next. From middle C, the perfect fourth is the 5th key up, F.
Every white-key fourth is perfect except F–B, which is a half step wider (the tritone). In a five-finger position it’s thumb to fourth finger.
On the white keys alone, the perfect fourths are C–F, D–G, E–A, G–C, A–D and B–E.
How a perfect fourth sounds
A perfect fourth sounds open and strong, like a call or a fanfare, but a little unfinished: the top note seems to want to settle down a step. It’s the sound of many opening pickups, where a melody leaps up onto the first strong beat.
In harmony, it’s a perfect interval: open and clear, though in some harmony it’s treated as needing to resolve.
Tunes that start with it
- Here Comes the Bride (Wagner’s Bridal Chorus) starts with a perfect fourth up.
- Amazing Grace starts with a perfect fourth up: “A-ma-” is D to G in G major.
- O Christmas Tree (O Tannenbaum) starts with a perfect fourth up.
- Mozart’s Eine kleine Nachtmusik opens with a perfect fourth down: G to D, and back up again.
Hum the tune’s first two notes and you have the interval: a quick way to sing one before you play it.
Where you’ll meet it
From the 5th note of a scale up to the home note is a perfect fourth (G up to C in C major), which is why so many melodies start that way: a pickup on the 5th, then the home note on the beat. It’s also the bottom of a second-inversion chord: G–C in G–C–E.
Turned upside down, with the bottom note moved up an octave, a perfect fourth becomes a perfect fifth: 5 and 7 half steps make an octave, and the letter numbers always add up to nine (4 + 5).
To read it fast in real music, practise intervals the way you read words: as shapes. Level 6: fourths and fifths in the free sight-reading exercises has plenty of them.
Quiz: the perfect fourth
Ten questions: name the interval on the staff, among its neighbours, and play a perfect fourth above a written note on the piano below, a MIDI keyboard or your computer keys.
The quiz needs JavaScript.
A perfect fourth above every note
| From | A perfect fourth up |
|---|---|
| C | F |
| C♯ | F♯ |
| D | G |
| E♭ | A♭ |
| E | A |
| F | B♭ |
| F♯ | B |
| G | C |
| A♭ | D♭ |
| A | D |
| B♭ | E♭ |
| B | E |
Each one is spelt with the 4th letter up, which is why some need a sharp or flat that looks unusual, like C♯ up to F♯.
Questions
How many half steps are in a perfect fourth?
5 half steps. Count every key, black and white, from the bottom note up to the top one: C to F is a perfect fourth.
What is a perfect fourth above C?
F. It’s spelt with the 4th letter up from C (C, D, E and F).
What is the inversion of a perfect fourth?
A perfect fifth. Move the bottom note up an octave and the five half steps become seven: perfect fourth and perfect fifth add up to an octave.
How do you recognise a perfect fourth on the staff?
One note is on a line and the other in a space: from a line, it lands in the second space up; from a space, on the second line up. That tells you the letter distance; then check the sharps, flats and key signature to tell perfect from augmented or diminished.
What song starts with a perfect fourth?
Here Comes the Bride (Wagner’s Bridal Chorus) starts with a perfect fourth up.
Hear every interval in real music
Pianomi, a free sight-reading app for piano, writes new pieces at your level and listens to your MIDI keyboard, so intervals become shapes you read without counting.