On the Edge: Sound Production on End-Blown Flutes
An analytical view of eight end-blown flutes is presented above (they will be referred to by the numbers 1 - 8, from left to right). Several basic ways in which the sound-producing edge, against which an airstream is directed, is situated on end-blown flutes are illustrated. Flutes 1 and 2 are both ring flutes (the ring has been detached from flute 1). On such flutes a shallow channel, terminating a short distance before the sound-producing edge, is dug out of the flute's surface and covered with a detachable ring to create a surface duct that automatically directs the airstream against the edge. Flutes 3 and 4 are duct flutes. A duct flute has an internal duct that directs the airsteam against a deeply-cut sound-producing edge located a few centimeters down the length of the instrument. Such flutes utilize the natural or drilled bore of the instrument, with the addition of some sort of extra plug or insert to create the channel for the airstream. Flutes 5 and 6 are notched flutes. Their sharp sound-producing edge is created by making an angled cut at the end of the tube. A player must direct the airstream very accurately against this edge in order to produce a sound. Flute 7 is a beveled flute. The rim of the tube is evenly filed away to produce a sharp edge around the entire circumference of the tube's bore. It is against this edge that the player directs the airstream. Flute 8 is a rim flute, where the end of the instrument's tube is simply cut off flat and air is directed against it.
(by Roger Vetter)