Overblowing
Overblowing is a technique used in playing a wind instrument to produce a different pitch by changing the direction and/or force of the air stream. Overblowing can be done deliberately in order to get a higher pitch, or inadvertently, resulting in the instrument producing a note other than the one intended.
In simple woodwind instruments, overblowing can cause a change into a different register. For example, in the Irish tin whistle, the player can play in the upper octave by using the same fingering as in the lower octave, but blowing harder.
In brass instruments, overblowing (sometimes combined with tightening of the embouchure) produces a different harmonic.
In instruments such as the saxophone, clarinet, oboe, or bassoon, the transition from lower to higher registers is aided by a "register hole" which encourages a vibration node at a particular point in the pipe, causing the vibration pattern to change, so overblowing is not so important.
Another type of overblowing is that used on instruments such as the flute, where the direction of the airstream is altered in order to sound higher notes. This technique can also be demonstrated when blowing across the top of a glass bottle (beer bottle, wine bottle, etc.) to produce a pitch. Overblowing can also be made easier by the use of a octave key which opens an extra hole.
Bagpipes
Overblowing is a problem that arises when playing the bagpipes. A phenomenon perhaps unique to piping, it is the most common reason for unsteady tone.
When a piper plays, a rhythm is set up between blowing into the blowstick and squeezing the bag. Often, a piper will over-squeeze the bag while still exhaling, causing the pipe to vary its tone.
Harmonica
In harmonica playing, overblowing is more complex than simply "blowing harder", and in fact overblow notes can be played as softly as any other note on the instrument. It requires a proper embouchure, such that the reed that normally only sounds during draw can be vibrated with blown air, and vice versa. If done properly, it will be a semitone higher than the normal note. Overblow notes are naturally flat but can be bent up to the correct pitch. An overblow consists of two steps: the direct reed must be choked (silenced), and the opposite reed must be sounded. A clean overblow note requires that both of these steps be executed simultaneously. Strong back pressure in the mouth, throat, and lungs is particularly important for overblowing. One common way to perform an overblow is to use a blow bend embouchure on a draw-bend only reed (hole 1-6), and to use draw bend embouchure on a blow bend only reed (hole 7-10). The latter technique is also known as the "overdraw" due to the reversed airflow, and these techniques are sometimes collectively referred to as "overbends". Certain modifications to factory-built harmonicas can increase the sensitivity of the instrument and make overblows far easier to achieve. Lowering the reed gaps and embossing the reed slots are the most common customization methods used to set up overblow-friendly harmonicas. Due to the fact that it involves both reeds in the chamber, overblowing is not possible on valved harmonicas (including chromatic harmonicas) or the Hohner XB-40, a harmonica with discrete reed chambers and extra sounding reeds.
The overblow and overdraw techniques allow the entire chromatic scale to be played on a diatonic harmonica. Howard Levy, a founding member of the Flecktones, was the first player to do so, although he was not the first to discover overblows. Today, overblowing is a common technique among advanced harmonica players, employed heavily by Jason Ricci, Carlos del Junco, Otavio Castro, Frédéric Yonnet [1] [2], and many other professional players.
Clarinet, saxophone, and oboe
In the case of the clarinet, the instrument's single reed vibrates against its mouthpiece, opening and closing the instrument's closed tube to produce a tone. When the instrument is overblown, with or without the aid of its register key, the pitch is a twelfth higher.
In the case of a saxophone, which has a similar mouthpiece-reed combination to the clarinet, or an oboe, where the two halves of the instruments double reed vibrate against each other, to the same effect. However, since the bore of these instruments are conical, the closed tube has the properties of an open tube; so when the saxophone or oboe is overblown, it jumps an octave higher.
References
- Kool, Jaap, Das Saxophon (The Saxophone). pub J. J. Weber, Leipzig. 1931; translated to English by Lawrence Gwozdz. Herts, England: Egon Publishers Ltd, 1987.
- Master Your Theory: 4th Grade by Dulcie Holand