Overblowing (a) A technique used while playing a wind instrument which, primarily through manipulation of the supplied air (versus, e.g., a fingering change or operation of a slide), causes the sounded pitch to jump to a higher one. Depending on the instrument (and less so on the player), overblowing may involve a change in air pressure, in the point at which the air is directed, or in the resonance characteristics of the chamber formed by the mouth and throat of the player (a feature of embouchure). In some instruments, overblowing may also involve the direct manipulation of the vibrating reed(s), and/or the pushing of a register key while otherwise leaving fingering unaltered. With the exception of harmonica overblowing, the pitch jump is from one vibratory mode of the reed or air column, e.g., its fundamental, to an overtone. Overblowing can be done deliberately in order to get a higher pitch, or inadvertently, resulting in the production of a note other than that intended.
In simple woodwind instruments, overblowing can cause the pitch to change into a different register. For example, a player of the Irish tin whistle can play in the upper octave by blowing harder while using the same fingering as in the lower octave.
In brass instruments, overblowing (sometimes combined with tightening of the embouchure) produces a different harmonic.
In beating, or striking, reed wind instruments such as the saxophone, clarinet, and oboe, the transition from lower to higher register is aided by a "register hole" which encourages a vibration node at a particular point in the pipe such that a higher harmonic is produced.
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.
Read more about Overblowing: Bagpipes, Harmonica, Woodwinds, Further Reading