Overtone
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An overtone is a sinusoidal component of a waveform, of greater frequency than its fundamental frequency. Usually the first overtone is the second harmonic, the second overtone is the third harmonic, etc.
Usage of term
Use of the term overtone is generally confined to acoustic waves, especially in applications related to music. Despite confused usage, an overtone is either a harmonic or a partial. A harmonic is an integer multiple of the fundamental frequency. A partial or inharmonic overtone is a non-integer multiple of a fundamental frequency.
An example of harmonic overtones:
| f | 440 Hz | fundamental tone | first harmonic |
| 2f | 880 Hz | first overtone | second harmonic |
| 3f | 1320 Hz | second overtone | third harmonic |
Not all overtones are necessarily harmonics, or exact multiples of the fundamental frequency. Some musical instruments produce overtones that are sharper or flatter than harmonics. The sharpness or flatness of their overtones is one of the elements that contributes to their sound; this also has the effect of making their waveforms not perfectly periodic.
Since the harmonic series is an arithmetic sequence (1f, 2f, 3f, 4f...), and the octave, or octave series, is a geometric sequence (f, 2×f, 2×2×f, 2×2×2×f, ...), this causes the overtone series to divide the octave into increasingly smaller parts as it ascends.
The overtones of a sound determine its sound quality or timbre and its frequency spectra.
Contrast with fundamental.
In barbershop music, the word overtone is often used in a different (though related) way. It refers to a psychoacoustic effect in which a listener hears an audible pitch that is higher than, and different from, the four pitches being sung by the quartet. This is not a standard dictionary usage of the word "overtone." The barbershopper's "overtone" is created by the interactions of the overtones in each singer's note (and by sum and difference frequencies created by nonlinear interactions within the ear).
See also
Source: originally from Federal Standard 1037C, but edited.cs:Alikvotní tón de:Obertöne nl:Boventoon he:צליל עילי