OVERTONE

in acoustics, faint tone sounding above the fundamental tone when a string or air column vibrates as a whole, producing the fundamental (first partial, or first harmonic); if it vibrates in sections, it produces overtones (upper partials, or harmonics). The listener normally hears the fundamental pitch clearly; with concentration he can hear the faint overtones. Harmonics are a series of overtones resulting when the partial vibrations are of equal sections (e.g., halves, thirds, fourths). As the vibrating sections become smaller, the harmonics are higher in pitch and successively closer together. The frequencies of the upper harmonics form simple ratios with the frequency of the first harmonic, or fundamental (e.g., 2:1, 3:1, 4:1). Some musical instrumentsamong them those whose sounds result from the vibration of metal, wood, or stone bars; of cylinders; of plates (e.g., cymbals, bells, marimbas); or of membranes (drums)produce nonharmonic overtones, or partialsthat is, tones the frequencies of which (and, therefore, the pitches of which) lie outside the harmonic series. Musical timbre, or tone colour, is greatly affected by the particular overtones favoured by a given instrument. Thus, the clarinet owes much of its mellow sound to lower overtones, as opposed to the more nasal oboe, which lacks them. See also combination tone.