, an octave
: eighth) or perfect octave
is the interval
between one musical pitch
and another with half or double its frequency
. 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".
It may be derived from the harmonic series
as the interval between the first and second harmonics.
Three commonly cited examples of melodies featuring the perfect octave as their opening interval are "Singin' in the Rain
", "Somewhere Over the Rainbow
", and "Stranger on the Shore
The octave has occasionally been referred to as a diapason
To emphasize that it is one of the perfect intervals
(including unison, perfect fourth
, and perfect fifth
), the octave is designated P8
. The octave above or below an indicated note
is sometimes abbreviated 8va
(= Italian all'ottava
), 8va bassa
(= Italian all'ottava bassa
, sometimes also 8vb
), or simply 8
for the octave in the direction indicated by placing this mark above or below the staff.