In this article I shall attempt to lay out the very basis of how music works in a straightforward, easily understood fashion. Please, if you’re a beginner, don’t be put off by the idea of learning and understanding anything about music. The basic stuff is really easy to grasp and will enhance your playing and following of what’s going on when you play with others. If you’re already into music this isn’t for you, it’s for those with no understanding at all.
Musical Notes – The Octave & Chromatic Scale
If you play a note and then double the frequency (ie the number of times a string vibrates in one second) you get the same note but higher. This is called an octave and can be heard on a ukulele if you play an open string and then count 12 frets up the fingerboard and play that note. It’s the same note an octave higher.
Listen to an octave being played from Wikipedia: