Technology / Home Audio / Octave: In audio, the interval between any two frequencies having a ratio of 2 to 1. One octave up from 100 Hz is 200 Hz, where one octave down from 100 Hz is 50 Hz. A harmonic is a doubling (2nd harmonic), tripling (3rd harmonic), quadrupling (4th Harmonic... Etc) of a fundamental frequency. Musical instruments (with the exception of electronic synthesizers) do not create pure tones. The fundamental (main frequency) is combined with its harmonics at various levels to create the sonic signature, or timbre of that instrument.
Science / Astrology / Higher Octave Planets: The three outermost planets, which symbolize the higher or spiritual level of expression in contrast to the lower or physical level symbolized by the inner planets with which they are linked. Uranus, MORE
Science / Astrology / Lower Octave Planets: Mercury, whose higher octave is Uranus; Venus, whose higher octave is Neptune; and Mars, whose higher octave is Pluto. Lower octave planets are associated with a lower or physical level or expression; MORE