Overtone
While the fundamental is usually heard most prominently, overtones are actually present in any pitch except a true sine wave.
[2] The relative volume or amplitude of various overtone partials is one of the key identifying features of timbre, or the individual characteristic of a sound.
When a resonant system such as a blown pipe or plucked string is excited, a number of overtones may be produced along with the fundamental tone.
Examples of exceptions include the circular drum – a timpani whose first overtone is about 1.6 times its fundamental resonance frequency,[5] gongs and cymbals, and brass instruments.
The human vocal tract is able to produce highly variable amplitudes of the overtones, called formants, which define different vowels.
[6] Most oscillators, from a plucked guitar string to a flute that is blown, will naturally vibrate at a series of distinct frequencies known as normal modes.
That is to say, the relative volumes of these overtones to each other determines the specific "flavor", "color" or "tone" of sound of that family of instruments.
However, some overtones in some instruments may not be of a close integer multiplication of the fundamental frequency, thus causing a small dissonance.
Due to phase inconsistencies[9] between the fundamental and the partial harmonic, this also has the effect of making their waveforms not perfectly periodic.
A tuning fork, provided it is sounded with a mallet (or equivalent) that is reasonably soft, has a tone that consists very nearly of the fundamental, alone; it has a sinusoidal waveform.
The first step in composing choral music with overtone singing is to discover what the singers can be expected to do successfully without extensive practice.
The overtones are also highly important in the tanpura, the drone instrument in traditional North and South Indian music, in which loose strings tuned at octaves and fifths are plucked and designed to buzz to create sympathetic resonance and highlight the cascading sound of the overtones.
Western string instruments, such as the violin, may be played close to the bridge (a technique called "sul ponticello[12]" or "am Steg") which causes the note to split into overtones while attaining a distinctive glassy, metallic sound.
Various techniques of bow pressure may also be used to bring out the overtones, as well as using string nodes to produce natural harmonics.
Likewise, when playing a harmonica or pitch pipe, one may alter the shape of their mouth to amplify specific overtones.
Each instrument can play (within their respective ranges) the notes of the overtone series in different keys with each fingering combination (open, 1, 2, 12, 123, etc).
[15] The French horn has a trigger key that opens other tubing and is pitched a perfect fourth higher; this allows for greater ease between different registers of the instrument.
Also, the overtone is very important in singing to take care of vocal tract shaping, to improve color, resonance, and text declamation.
[19][20][21] Because the overtone series rises infinitely from the fundamental with no periodicity, in Western music the equal temperament scale was designed to create synchronicity between different octaves.
In the 20th century, exposure to non-Western music and further scientific acoustical discoveries led some Western composers to explore alternate tuning systems.
For example, in Grisey's seminal work Partiels, the composer used a sonogram to analyze the true sonic characteristics of the lowest note on a tenor trombone (E2).
[2] Other spectralists and post-spectralists include Jonathan Harvey, Kaija Saariaho, and Georg Friedrich Haas.
John Luther Adams is known for his extensive use of the overtone series, as well as his tendency to allow musicians to make their own groupings and play at their own pace to alter the sonic experience.
Everything That Rises is a piece for string quartet that has sixteen harmonic clouds that are built off of the fundamental tone (C0)[28]
