Octave
Two notes an octave apart — heard as the same pitch class at two heights
Related
An octave is the distance between two notes whose frequencies are in a 2:1 ratio. C4 to C5 is an octave; 440 Hz to 880 Hz is an octave. The ear hears the two as "the same pitch class at two heights" — octave equivalence: they share a note name but sit in different registers.
The octave is the most stable consonance, and nearly every musical system treats it as the "repeat unit" of pitch. The usual mistake is to read it as "eight notes": C to the next C does cross eight note names, but the distance is twelve semitones, not eight.
Read deeper → Octave
Sources
- 八度的频率比与听觉等价性，参 The New Grove Dictionary of Music and Musicians, "Octave"；本文为原创表述
Used for fact-checking only; all prose is original.