Harmonics

Harmonics are vibrations at frequencies that are multiples of the fundamental. They are characterized as even-order and odd- order harmonics. For instance, the "second-order harmonic" is the fundamental frequency multiplied by two, and is an even-order harmonic. Each even-order harmonic is one octave or x octaves higher than the fundamental; they are therefore musically related to the fundamental. Odd-order harmonics create a series of notes that are not musically related to the fundamental frequency, and therefore may have an unpleasant sound. Harmonics are also called "overtones" or "partials".