Harmonics refers to the complete set of sounds produced by a musical note. Every musical tone consists of a blend of the note sounded and higher tones related to it. The actual note sounded is called the fundamental. The other tones are called its overtones. A fundamental and its overtones always harmonize (blend well together).
The vibrations of a string or of an air column produce musical sounds. For example, when a note is played on a piano, the entire string vibrates to produce the fundamental. But it also vibrates in separate sections called partials. Each half of the string vibrates separately, each third vibrates separately, and so on. These separate vibrations produce tones of a higher pitch than the fundamental. They move in a regular series. The separate vibration in two equal parts produces the octave, a note that is eight notes higher than the fundamental. The vibration of three equal parts produces the dominant, a fifth above the octave. The vibrating string may divide many times, but each division makes the overtone softer.
Instruments and voices differ in quality and loudness, largely because of the number and distribution of the overtones they produce. The human voice is richer in overtones than most instruments.
Loud instruments produce the higher harmonics. The tone quality is soft and flutelike when the fundamental tone and the lower harmonics are present. A combination of tones up to the sixth harmonic makes a rich, full sound.
