 The Clarinet BBoard
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Author: kdk
Date: 2013-05-24 18:12
The ongoing thread about undercutting suggests something I've often wondered about. Undercutting on a clarinet is done to free a stuffy note and/or sharpen the pitch of a flat note. Typically, the flatness that the undercutting is meant to correct isn't the same in all registers - C#4 might be uncomfortably flat and stuffy and the decision may be to undercut the hole to correct the problem, but care always has to be taken because G#5 is typically not as flat to begin with, so a compromise may have to be made and the C# left a little flat in order not to raise the G# too much. The same often happens with E4, which is often flat and B5, which is often very sharp to start with. Bringing E4 up to be perfectly in tune may make B5 almost untuneable. Also F4/C6 and sometimes A3/E5.
So my question is, why don't the same fingerings in each register have the same pitch tendencies? Why is T XOO OOO often so much flatter relative to its surrounding notes than RT XOO OOO? My only explanation is that the register tube diameter on the clarinets I've played (Buffets and Selmer 10Gs), since it must also function to produce a usable Bb4, is somehow out of proportion to the length of the vibrating air column and not only serves as a pressure vent but actually changes the volume of vibrating air relative to that of E4 (when the vent is closed). I'm not sure if I've described that clearly or not.
Are there other acoustical factors that cause this phenomenon (flat E4/sharp B5, flat F4/sharp C6)?
Tangentially, do clarinets with different designs for producing throat Bb without opening the register vent, like Mazzeo or, more recently, Patricola instruments, use a smaller register vent, and do those clarinets exhibit the same differences in chalumeau and clarion intonation for specific fingerings?
Karl
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Author: David Spiegelthal ★2017
Date: 2013-05-24 18:30
Read Arthur Benade's book on musical instrument acoustics --- among other things it discusses how the standing wave created during the playing of a note actually extends beyond the lowest open tonehole, while the amount it extends past depends on the frequency --- so although the same set of toneholes are open for a lower note and its upper twelfth, the effective lengths of their standing waves are not exact multiples/fractions of each other. Hence a modification that affects one note won't affect its upper or lower twelfth by the same proportion.
This effect is why a vent hole drilled in the bell raises the pitch of the low chalumeau E/F proportionally more than it does their upper twelfths, the low clarion B/C.
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Author: rtmyth
Date: 2013-05-24 20:33
Consult Benade's book. Backun and Ridenour, among other designers, could also answer these questions.
richard smith
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Author: Steven Ocone
Date: 2013-05-24 21:22
The term mentioned above is called end correction. The acoustical length of a cylinder is longer than the actual length. The distance the standing wave extends past the first open tone hole depends on the frequency as well as the size, depth, shape of the tone hole and often on where the next open tone hole is. As well as I understand it anyway.
Steve Ocone
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