Overtone

An overtone is any resonant frequency above the fundamental frequency of a sound (or of any oscillation). An overtone may or may not be a harmonic. In other words, overtones are all pitches higher than the lowest pitch within an individual sound; the fundamental is the lowest pitch. While the fundamental is usually heard most prominently, overtones are actually present in any pitch except a true sine wave. The relative volume or amplitude of various overtone partials is one of the key identifying features of timbre, or the individual characteristic of a sound. The human vocal tract is able to produce highly variable amplitudes of the overtones, called formants, which define different vowels.

Using the model of Fourier analysis, the fundamental and the overtones together are called partials. A harmonic partial is a partial whose frequency is an integer multiple of the fundamental (including the fundamental, which is 1 times itself), while the frequency of an inharmonic partial is not an integer multiple of the fundamental. These overlapping terms are variously used when discussing the acoustic behavior of musical instruments. While the nth harmonic may sometimes be called the (n-1)th overtone, ANSI/ASA S1.1-2013 has deprecated the use of the term "overtone" in favor of "harmonic" to reduce ambiguity.