In music, an octave (sometimes abbreviated 8ve or P8) is the interval between one musical pitch and another with half or double its frequency. Examples For example, if one note has a frequency of 400 Hz, the note an octave above it's at 800 Hz, and the note an octave below is at 200 Hz. The ratio of frequencies of two notes an octave apart is therefore 2:1. Further octaves of a note occur at 2n times the frequency of that note (where n is an integer), such as 2, 4, 8, 16, etc. and the recipro… (More on Octave)