Octave

Perfect octave
Inverse	unison
Name
Other names	-
Abbreviation	P8
Size
Semitones	12
Interval class	0
Just interval	2:1
Cents
12-Tone equal temperament	1200
Just intonation	1200

${ \override Score.TimeSignature#'stencil = ##f \relative c' { \clef treble \time 4/4 \key c \major <c c'>1 } }$

A perfect octave between two Cs

In music, an octave (Latin: octavus: eighth) or perfect octave (sometimes called the diapason)^[2] is a series of eight notes occupying the interval between (and including) two notes, one having twice the frequency of vibration of the other. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems".^[3]^[4] The interval between the first and second harmonics of the harmonic series is an octave. In Western music notation, notes separated by an octave (or multiple octaves) have the same name and are of the same pitch class.

To emphasize that it is one of the perfect intervals (including unison, perfect fourth, and perfect fifth), the octave is designated P8. Other interval qualities are also possible, though rare. The octave above or below an indicated note is sometimes abbreviated 8^a or 8^va (Italian: all'ottava), 8^va bassa (Italian: all'ottava bassa, sometimes also 8^vb), or simply 8 for the octave in the direction indicated by placing this mark above or below the staff.

^ ^a ^b ^c Duffin, Ross W. (2008). How equal temperament ruined harmony : (and why you should care) (First published as a Norton paperback. ed.). New York: W. W. Norton. p. 163. ISBN 978-0-393-33420-3. Archived from the original on 5 December 2017. Retrieved 28 June 2017.
^ William Smith & Samuel Cheetham (1875). A Dictionary of Christian Antiquities. London: John Murray. ISBN 9780790582290. Archived from the original on 2016-04-30.
^ Cooper, Paul (1973). Perspectives in Music Theory: An Historical-Analytical Approach, p. 16. ISBN 0-396-06752-2.
^ "Dictionary.com | Meanings & Definitions of English Words". Dictionary.com. Retrieved 2024-01-24.

[Duffin-1] Duffin, Ross W. (2008). How equal temperament ruined harmony : (and why you should care) (First published as a Norton paperback. ed.). New York: W. W. Norton. p. 163. ISBN 978-0-393-33420-3. Archived from the original on 5 December 2017. Retrieved 28 June 2017.

[2] William Smith & Samuel Cheetham (1875). A Dictionary of Christian Antiquities. London: John Murray. ISBN 9780790582290. Archived from the original on 2016-04-30.

[3] Cooper, Paul (1973). Perspectives in Music Theory: An Historical-Analytical Approach, p. 16. ISBN 0-396-06752-2.

[4] "Dictionary.com | Meanings & Definitions of English Words". Dictionary.com. Retrieved 2024-01-24.

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