Original article: http://www.soundonsound.com/sos/sep03/articles/synthsecrets.htm
The Monty Python team once famously claimed that being able to play the flute was a simple matter of 'blowing here, and moving your hands up and down here'. But there's a lot more to it than that... This is the 53rd article in a 63-part series. Read all parts.
Gordon Reid
Last month I discussed the sound of the pan flute, leaving you with a diagram that showed how you could use a large modular synth to create a remarkably accurate simulation of the instrument. Successful though it was, the patch was a monster, and not one you could create on any basic (read... easily affordable) synth. This month, we'll look at another of the flute family, and see whether we can synthesize it using something rather simpler.
But first, I want to take a look at the Japanese Shakuhachi. Made from a single piece of bamboo, this is another instrument that requires you to blow over an aperture, but it differs from its more primitive cousin in three ways.
Firstly, you excite the air by blowing over a sharp edge at the mouth of the pipe. If you consider Figure 1 (below) you can see an instance when a jet of air blown against such an edge is deflected downward. At that moment, the part of the stream shown in orange is moving minutely faster than that shown in red, so the air pressure on the flow tends to press it upward. This is the principle that keeps aeroplanes in the sky: air moving faster over the top surface of the wing generates less pressure than that moving more slowly along the shorter underside. The net effect is therefore an upward pressure that lifts the machine off the ground.
If the upward pressure in Figure 1 is sustained for a fraction of a second, the jet is pushed upward, and we soon reach the situation shown in Figure 2. Now, the net atmospheric pressure is downward, and we quickly move back to the situation shown in the first diagram.
Figure 1: The pressure exerted when air passes under a sharp edge placed in the stream.
Figure 1: The pressure exerted when air passes under a sharp edge placed in the stream.