A Dictionary of Music and Musicians/Over-blowing

OVER-BLOWING is the production of a higher note than the natural note of a pipe, by forcing the wind. In the flute the upper octaves are legitimately so produced. In the organ it is apt to arise when the feeders of a bellows pump wind into the reservoir in greater quantities or at greater speed than its consumption, and when the reservoir is therefore liable to become more than sufficiently full. If more wind were then to be supplied it might become more compressed,—stronger,—causing the pipes to produce a momentary scream rather than a musical sound. To prevent this natural consequence of 'overblowing,' a safety-valve or waste-pallet is provided, which allows the superadded wind to pass from the reservoir.

[ E. J. H. ]