Overtone
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An overtone is a sinusoidal component of a waveform, of greater frequency than its fundamental frequency. The term is usually used in music, rather than wave physics. (see standing wave)
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[edit] Explanation
Most oscillators, from a guitar string to a bell (or even the hydrogen atom or a periodic variable star) will naturally vibrate at a series of distinct frequencies known as normal modes. The lowest frequency normal mode is known as the fundamental frequency, while the higher frequencies are overtones. Often, when these oscillators are excited, by, for example, plucking a guitar string, it will oscillate at several of its frequencies at the same time. In music, this gives the sensation of hearing other frequencies (overtones) above the lowest frequency (the fundamental). The overall combination of the instrument's specific overtones is what determines the timbre ("flavour of sound") of that instrument. Timbre is what gives the listener the ability to distinguish different instruments that play the same note at the same volume in a band or orchestra.
A driven non-linear oscillator, such as the human voice, a blown wind instrument, or a bowed violin string (but not a struck guitar string or bell) will oscillate in a periodic, non-sinusoidal manner. This generates the impression of sound at integer multiple frequencies of the fundamental known as harmonics. For most string instruments and other long and thin instruments such as a trombone or bassoon, the first few overtones are also integer multiples of the fundamental frequency, producing a perfect harmonic series. Thus, in music, overtones are often called harmonics. Depending upon how the string is plucked or bowed, different overtones can be emphasized.
However, some overtones in some instruments may not be of an exact integer multiplication of the fundamental frequency, thus causing a small dissonance. "High quality" instruments are usually built in such a manner that their individual notes do not create disharmonious overtones.
The intensity of each of the overtones is rarely constant during the duration of the overall sound. Over time, different overtones may decay at different rates causing the relative intensity of each overtone to rise or fall independent of the overall volume of the sound, and a carefully trained ear can hear these changes even in a single note. This is why the timbre of a note may be perceived differently when played staccato or legato, dampened or lengthened.
[edit] Musical usage term
An 'overtone' is a partial (a "partial wave" or "constituent frequency") that can be either a harmonic or an inharmonic. A harmonic is an integer multiple of the fundamental frequency. An inharmonic overtone is a non-integer multiple of a fundamental frequency.
An example of harmonic overtones: (absolute harmony)
| f | 440 Hz | fundamental tone | first harmonic |
| 2f | 880 Hz | first overtone | second harmonic |
| 3f | 1320 Hz | second overtone | third harmonic |
| 4f | 1760 Hz | third overtone | fourth harmonic |
Not all overtones are necessarily harmonics, or exact multiples of the fundamental frequency. Some musical instruments produce overtones that are slightly sharper or flatter than the true harmonics. The sharpness or flatness of their overtones is one of the elements that contributes to their unique sound. This also has the effect of making their waveforms not perfectly periodic. Some instruments, such as tuning forks or flutes produce a clear or near perfect sound because their overtones are in very good approximation of "absolute" harmony with the base frequency.
[edit] Type of music
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). Similar effects can be found in other a capella polyphonic music such as the music of the Republic of Georgia.
[edit] String instruments
String instruments can also produce multiphonic tones when strings are divided in two pieces. The most well-known technique is playing flaegolet tones on a guitar. Other multiphonic extended techniques used are prepared piano, prepared guitar and 3rd bridge guitar. Experimental luthier Yuri Landman created a 12-string overtone zither called the Moodswinger.
[edit] Overtone singing
Overtone singing, also called harmonic singing, occurs when the singer amplifies voluntarily two overtones in the sequence available given the fundamental tone he/she is singing. Overtone singing is a traditional form of singing in many parts of the Himalayas; Tibetans, Mongols and Tuvans are known for their overtone singing. Also, harmonics change the overtones.
[edit] See also
- Harmonic series (music)
- Just intonation
- Xenharmonic
- Stretched octave
- 3rd bridge guitar
- Moodswinger, overtone guitar
[edit] External links
