en

Intervals

Unison

1P · no semitones

Two notes at the same pitch — the interval you hear when a section plays in unison.

Also written P1 · 1P

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Unison

1P · no semitones

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Play it on your instrument
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From
On the piano, from every note
FromNotesPlay it on your instrument
CC – C
C#C# – C#
DD – D
EbEb – Eb
EE – E
FF – F
F#F# – F#
GG – G
AbAb – Ab
AA – A
BbBb – Bb
BB – B

Tap a key or a fret to hear it.

Number and quality

An interval has two names. The number counts the letter names from the lower note to the upper one, and the quality counts the semitones inside that number. Unison spans one letter name, which makes it a unison, and no semitones, which makes it perfect.

  2. no semitones

Read on: number and quality · half steps and whole steps · inversion · compound intervals · consonance and dissonance

Every unison

A unison can take these qualities, one semitone apart; choose one to see the upper note move and hear the pair.

  2. Open Augmented Unison →

Where it lives

Unison is in every chord whose formula includes 1P from the root, in every scale that includes it from the tonic, and between these pairs of notes in a major key.

Chords built with it

  • CC · E · G

  • CmC · Eb · G

  • C5C · G

  • C7C · E · G · Bb

  • Cmaj7C · E · G · B

  • Cm7C · Eb · G · Bb

  • CmMaj7C · Eb · G · B

  • Cm7b5C · Eb · Gb · Bb

  • CdimC · Eb · Gb

  • Cdim7C · Eb · Gb · Bbb

  • CaugC · E · G#

  • Csus2C · D · G

  • Csus4C · F · G

  • C7sus4C · F · G · Bb

  • C6C · E · G · A

  • Cm6C · Eb · G · A

  • C6/9C · E · G · A · D

  • C9C · E · G · Bb · D

  • Cmaj9C · E · G · B · D

  • Cm9C · Eb · G · Bb · D

  • C11C · G · Bb · D · F

  • Cm11C · Eb · G · Bb · D · F

  • C13C · E · G · Bb · D · A

  • Cmaj13C · E · G · B · D · A

  • Cm13C · Eb · G · Bb · D · A

  • Cmadd9C · Eb · G · D

  • Cadd9C · E · G · D

  • C7b9C · E · G · Bb · Db

  • C7#9C · E · G · Bb · D#

  • C7#5C · E · G# · Bb

  • Calt7C · E · Bb · Db

Scales that contain it

In C major

  • C–C
  • D–D
  • E–E
  • F–F
  • G–G
  • A–A
  • B–B

Related intervals

The intervals one step from Unison: its inversion, the same sound spelled differently, its simple or compound form, and its nearest neighbours in size.

  • Diminished Second2d · no semitones · C – Dbb

    The same sound, spelled differently

  • Octave8P · 12 semitones · C – C

    The compound form, an octave wider

  • Minor Second2m · 1 semitone · C – Db

    One size away

  • Major Second2M · 2 semitones · C – D

    One size away

Open it in a tool

Understanding Unison

Names and symbols

Unison is written P1, 1P: the letter is the quality, the number the size. Chord formulas on this site write the number first, as tonal does.

A unison is the interval of no distance, and it still has a quality: raise one of the two notes and it is an augmented unison, a chromatic half step that keeps its letter. A diminished second is the same distance written with two letters, C to D♭♭, which almost never happens outside theory exercises.

How it sounds

A unison is zero semitones: C – C. Played together the two parts fuse into a single, reinforced tone, which is why doubling a melody at the unison thickens it without changing its harmony.

Perfect unisons are the reference every other interval is measured against. When two instruments are slightly out of tune the unison is where you hear it first, as a slow beating that speeds up the further apart they drift.

Where you will meet it

Orchestral tutti passages, guitar doubling, and octave-and-unison riffs in rock all rely on it. In tuning, a unison against a reference pitch is the standard test.

Learn this properly

Chapter 5: Intervals

Common questions

How many semitones is a Unison?
A Unison spans 0 semitones — the same pitch sounded twice. Count the semitones of any interval with the interval calculator.
Is a unison an interval at all?
Yes. It is the interval of zero distance, and it behaves like one: it can be perfect, augmented or diminished depending on spelling.
What is the difference between a unison and an octave?
A unison is the same pitch; an octave is the same pitch class twelve semitones apart. Both sound like "the same note", but only the unison has no distance.
How do I play Unison?
On guitar the handiest shape is Next string, G 5 · B 1, read as string and fret; the instrument panel draws it from any starting note with the other shapes. On the piano count no semitones up from any key, black keys included. Play the notes together for the harmonic form, one after the other for the melodic form.
What is the inversion of Unison?
The inversion of Unison is the Unison: put the lower note an octave higher and the distance that remains is the inversion. The two always add up to an octave, no semitones and no semitones, and swap their qualities between major and minor, or keep perfect as perfect.

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