There was a man who lived about 2500 years ago who sought to find out what made musical sounds so interesting, especially the relationship between two important notes. His name was Pythagorus. He plucked a string to study sound, then found out some of the magic.
When you make the second string vibrate twice as fast as the first, the new sound you make almost disappears.
He created the series of notes we all learn as “Do, Re, Mi…”. The two most pleasing notes were the two Dos. We call it the OCTAVE today.
Why that is so interesting, and much more, will be explained in the following chapters.