Harmonic series (music)

Pitched musical instruments are usually based on a harmonic oscillator such as a string or a column of air. Both can and do oscillate at numerous frequencies simultaneously. Because of the self-filtering nature of resonance, these frequencies are mostly limited to integer multiples of the lowest possible frequency, and such multiples form the harmonic series.

Register and special effects of musical instruments

In wind instruments, which produce sounds with a resonating air column, the lowest possible note is the fundamental resonance of the entire instrument. For a given length of resonator, only notes in the harmonic series of the resonator can be played clearly: higher notes are played by exciting higher harmonics, which is accomplished by changing the vibration at the reed or mouthpiece. Notes that are not in the harmonic series are played by changing the effective length of the resonator, usually by opening a venting hole in the side of the instrument.

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Many wind instruments are designed to allow higher harmonics to be played more easily by damping the normal fundamental resonance. For example, on most woodwind instruments (such as clarinet, saxophone, oboe, and bassoon), an octave key or register key opens a small hole high up on the resonator, prompting the instrument to oscillate at a higher harmonic partial and giving the player easier access to a higher octave of the instrument. Generally, flautists can access higher harmonics even without a register key simply by changing the pressure and angle of the air stream. This is also evident in blowing over the lips of bottles.

Related Topics:
Woodwind instruments - Clarinet - Saxophone - Oboe - Bassoon - Octave key

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On brass instruments, the small number of keys only allows a small chromatic range to be played off of any given harmonic, so it is necessary for the musician to play many harmonics to get the full range of the instrument. The different harmonics are accessed by increasing the vibration of the lips against the mouthpiece, essentially by tightening the embouchure and blowing the air faster. A brass instrument of relatively short length with no valves (e.g. military bugle) plays only the lowest notes of the harmonic series, making it ideal for bugle calls. The six- to ten-foot length of the unvalved "natural trumpet", the predominant form of the trumpet from about 1500 to the early 1800shttp://www.goucher.edu/physics/baum/nattrumpfaql.htm, not only allowed skilled players to play twice as many harmonics (the "Clarino register"), but also produced a fuller, richer tone due to the presence of those harmonics in lower notes.

Related Topics:
Brass instruments - Bugle - Bugle call - Trumpet

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For cylindrical-bore brass instruments such as the modern trumpet and trombone, the second harmonic is the lowest playable note. The fundamental is technically playable, but it is difficult and does not sound musical. On a conical-bore brass instrument such as flugelhorn or tuba, the fundamental is available only as a special note called a "pedal tone" or "pedal note" and is rarely called for in written music.

Related Topics:
Trumpet - Trombone - Flugelhorn - Tuba

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On a stringed instrument, it is possible to damp the fundamental and thus sound at a higher frequency by lightly touching the string at a harmonic node. For example, by touching the string lightly at its midpoint, the musician forces the string to vibrate in its second transverse mode, sounding the second harmonic. Such light-touch fingering can be applied to notes at 1/3, 1/4, etc. of the string length to produce higher harmonics. Simply pressing the string to the fingerboard at those positions would not yield the same note as the harmonic.

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