Overtone

An overtone is a sinusoidal component of a waveform, of greater frequency than its fundamental frequency.

Use of the term overtone is generally confined to acoustic waves, especially in applications related to music.

The first overtone is usually roughly twice the frequency of the fundamental, and thus then corresponds to the second harmonic; the second overtone is usually roughly three times the frequency of the fundamental, and thus then corresponds to the third harmonic, etc.

Unlike harmonics, overtones are not necessarily exact multiples of the fundamental frequency. Not all musical instruments have overtones that match their harmonics, as described earlier in this note. 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 overtone series is an arithmetic series (f+1+1+1...), and the octave, or octave series, is a geometric series (f×2×2×2...), this causes the overtone series to divide the octave into more and more smaller parts as it progresses.

Contrast with fundamental, harmonic.

See also musical tuning, harmonic series, harmony, just intonation.

Source: originally from Federal Standard 1037C, but edited.