Ganassi - Kynsecker - Bressan - Denner
Structural differences and their effects on musical practice
Lecture held at the ERTA Symposium, Karlsruhe 1994 English translation by Terry Simmons, Warrnambool, Australia
1 Fundamental of Recorder acoustics
The aim of this paper is to examine recorders regarding different building methods: the structural and constructional side, how structural differences affect the musical characteristics; and ranges of application of the instrument.
1.1 Relationship of Bore Profile to Tone Colour
We will examine the various factors-determining the instrument’s sound, beginning with the different profiles of the bore. Here the differences are e.g. between a Renaissance recorder, shown at its clearest in the Ganassi building method.
From elementary physics or from organ-building, we know the difference between open and stopped pipes. We know that for a given frequency, a stopped pipe is only half as long as an equivalent open pipe. Also the tone quality is different. We know that the sound of an instrument consists of the fundamental plus different partial tones. After the fundamental as the basis, the octave follows as the second, above that the fifth in addition (and/or the twelfth to the fundamental) as the third, as the fourth the double octave, as the fifth a third above that as the sixth again a fifth above the double octave and so on.
We remember that whereas the sound of an open pipe consists of all of the harmonics, the sound of a stopped pipe is comprised of the odd-numbered harmonics only: the fundamental, fifth above the octave, third above the double octave , etc. We call this rather nasal-sounding tone picture “stopped tone quality”.
Stopped pies also differ from open pipes in their over-blowing behavior. Stopped whistles can be over-blown only into odd-numbered harmonics. The typical representative is the clarinet, which cannot be overblown into the octave, but straight into the twelfth.
Between these two extremes are pipes in which the bore more or less strongly contracts towards the bottom end. In such whistles the even-numbered partials are suppressed - completely, but clearly weakened compared with the odd-numbered, so that such pies have a tendency towards a nasal or “stopped: tone quality, even though it is generally easily possible in all rule to over-blow them to the octave over a wide range.
A further factor is the bore diameter compared to the its length. The narrower the bore, the more strongly pronounced are the higher harmonics and the more easily the instrument can be overblown. In extreme cases it may be difficult to produce low notes because of the instrument’s strong tendency to over-blow. By contrast, an instrument with a relatively wide bore has, by virtue of its large air volume, a large sound, is rather poor in overtones and perhaps rather difficult to over-blow into higher harmonics.
1.2 Other sound-Determining design features
Naturally there are other design factors that play a large role in determining the sound of a recorder.
There is first the design of the “cut up”. Generally one can say that the higher it is, the louder and more direct the sound becomes. (The cut-up is the distance from the wind-way exit to the edge.)
This is particularly relevant in relation to the bore diameter. This becomes clearest, if one looks at the extreme. Thus a wide bore together with a low cut-up results in a dark, intimate sound, while a narrow bore, combined with large cut-up results in strident instruments with fast, nervous speech.
As well, there are clear differences in the direction of the wind-way in relation to the instrument’s length axis. Generally a wider bore needs to be stimulated stronger than than more narrow bores. Consequently with Renaissance instruments the windway is almost always angled slightly inwards, while with the usually narrower-bore baroque instruments they are normally parallel or even angled slightly outward the instrument.