Perfect unison

Perfect unison: C#, 0 semitones; perfect consonance.

Octaves

Theory

General info

Interval: Perfect unison
Quality: Perfect
Semitones: 0
Degree distance: 1 degree
Degree: 1

Interval structure

Lower note: C# (277.2 Hz)
Degree formula: I
I
Semitone formula: 0 semitones

Interval construction

Interval formula: P1
Brief explanation: A perfect unison joins two sounds at the same pitch and spans zero semitones. It may occur through unison doubling or repetition of one note.

Interval notes

1C#root

Consonance / dissonance

Sonority: Perfect consonance
Explanation: A perfect unison is a perfect consonance. Matching pitch creates no intervallic dissonance, although two sources may differ in timbre and loudness.

How the interval sounds

A unison joins two sounds at the same pitch and spans zero semitones. When sounded together, pitch remains the same while timbre and loudness may differ.

Famous example:

Any held note — the root of a key

Tendencies & resolutions

A unison does not require resolution by itself. Moving either voice changes it into another interval whose function comes from harmonic context.

Interval inversion

Inverts to: OctaveP8
Quality change: Perfect
perfect
Inversion rule: When inverting unison, the upper note moves up an octave. Unison inverts to an octave: P1 → P8.

Related intervals

Close intervals

m2Minor 2nd

Appears in chords

C#Major C#Minor C#Dominant 7 C#Major 7 C#Minor 7 C#Diminished C#Augmented C#Diminished 7th C#Augmented 7th C#Half-dim 7

Appears in scales & modes

C#Ionian (major)C#Dorian C#Phrygian C#Lydian C#Mixolydian C#Aeolian (natural minor)C#Locrian

This interval on guitar 🎸

See how Perfect unison looks on guitar.

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