Perfect Unison
Definition & Properties
The perfect unison is the interval between two identical pitches. It represents zero distance and is the most consonant interval possible — two voices in complete agreement.
| Property | Value |
|---|---|
| Abbreviation | P1 |
| Semitones | 0 |
| Quality | Perfect |
| Just Ratio | 1:1 |
| Cents from Equal | 0 |
| Harmonic Character | perfect consonance |
Ear Training Reference
The Perfect Unison (P1) is commonly recognized by the either motion of: Same pitch (no movement).
Practice direction: either — sing from the lower note down by 0 semitones.
Note Pair Examples
| Note 1 | Note 2 | Interval | Semitones |
|---|---|---|---|
| C | C | Perfect Unison | 0 |
| G | G | Perfect Unison | 0 |
| D | D | Perfect Unison | 0 |
| F | F | Perfect Unison | 0 |
Intonation by Temperament
The Perfect Unison measures 1:1 in just intonation (0 cents from equal temperament). This deviation affects ensemble tuning and instrument voicing.
| Temperament | C4 (Hz) | C4 (Hz) |
|---|---|---|
| Equal Temperament | 261.626 | 261.626 |
| Pythagorean | 260.740 | 260.740 |
| Just Intonation | 261.626 | 261.626 |
Instrument Tuning Context
Unisons appear in ensemble tuning — two instruments playing the same pitch. Even slight mistuning creates audible beats.
Chords & Scales Containing This Interval
The Perfect Unison is present in all diatonic contexts. See the Chord Reference for chord types that incorporate this interval.
Scales
These scales include the Perfect Unison as a structural interval: