The perfect fourth
- C1
- F4
A perfect fourth is five semitones, from C to F. Inverted, with the lower note moved up an octave, it becomes the perfect fifth.
Its short name is P4. Counted in letters, it spans four letter names, which is why it is written C to F rather than with another name for the same pitch.
The perfect fourth on bass
On bass, the perfect fourth is the same fret when you cross to the next string, and five frets up along one string.
Every pair of neighbouring strings gives the same shape, because the strings of this tuning are evenly spaced. Once you have learned the shape, it works anywhere on the neck.
On the staff
On a bass staff, the two notes are written C and F.
The staff shows the two notes one after the other, then together. C to F spans four letter names, which is what the interval's name counts. What you hear is a distance of five semitones.
On the keyboard
A keyboard makes this distance easy to see, where a fretboard hides it. The upper note is five keys along from the lower one, counting black and white keys alike.
C and F on the whole neck
14 notes are marked across four strings.
This diagram marks both notes of the perfect fourth, C and F, everywhere they fall on bass. You can find every pair shown above somewhere on it.
A perfect fourth above every note
| From | A perfect fourth up |
|---|---|
| C | F |
| D♭ | G♭ |
| D | G |
| E♭ | A♭ |
| E | A |
| F | B♭ |
| F♯ | B |
| G | C |
| A♭ | D♭ |
| A | D |
| B♭ | E♭ |
| B | E |
C–F, D♭–G♭, D–G, E♭–A♭, E–A, F–B♭, F♯–B, G–C, A♭–D♭, A–D, B♭–E♭, B–E
The shapes above do not change with the key, which is the reason to learn an interval as a shape. Only the note names change, and this table gives them for every starting note.