Overtone

The first overtone is usually twice the frequency of the fundamental, and thus then corresponds to the second harmonic; the second overtone is usually three times the frequency of the fundamental, and thus then corresponds to the third harmonic, etc. Not all musical instruments have overtones that match the harmonics as described in this note.

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

Contrast with fundamental, harmonic.

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