Perfect Fourth
Definition & Properties
The perfect fourth is a strong consonance in melody but carries mild instability in two-voice harmony where it requires resolution. It is the basis of quartal harmony in jazz.
| Property | Value |
|---|---|
| Abbreviation | P4 |
| Semitones | 5 |
| Quality | Perfect |
| Just Ratio | 4:3 |
| Cents from Equal | -1.96 |
| Harmonic Character | consonance (mildly unstable in harmony) |
Ear Training Reference
The Perfect Fourth (P4) is commonly recognized by the ascending motion of: Here Comes the Bride; Amazing Grace.
Practice direction: ascending — sing from the lower note up by 5 semitones.
Note Pair Examples
| Note 1 | Note 2 | Interval | Semitones |
|---|---|---|---|
| C | F | Perfect Fourth | 5 |
| G | C | Perfect Fourth | 5 |
| D | G | Perfect Fourth | 5 |
| F | A# | Perfect Fourth | 5 |
Intonation by Temperament
The Perfect Fourth measures 4:3 in just intonation (-1.96 cents from equal temperament). This deviation affects ensemble tuning and instrument voicing.
| Temperament | C4 (Hz) | F4 (Hz) |
|---|---|---|
| Equal Temperament | 261.626 | 349.228 |
| Pythagorean | 260.740 | 347.654 |
| Just Intonation | 261.626 | 348.834 |
Instrument Tuning Context
Intervals smaller than a perfect fifth (5 semitones) are most sensitive to tuning in ensemble playing. Wind and string players adjust embouchure and finger pressure to lock in pure ratios.
Chords & Scales Containing This Interval
Chords
These chord types contain the Perfect Fourth as a characteristic interval:
Scales
These scales include the Perfect Fourth as a structural interval: