Tonal System
From Wiki Notes @ WuJiewen.com, by Jiewen Wu
Music notes are made of sound (evenly-spaced) waves. To measure how high or low a sound is, musicians use the note's pitch instead of frequency. Notes are also named, e.g., musicians call the note with frequency "440 vibrations per second" an "A".
Octave: any note that is twice the frequency of another note is one octave higher. Notes that are one octave apart (higher or lower) are of the same name.
