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Distinguished Technician & SOTW Columnist. RIP, Yo
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I've read up on how crescents work (on musicmedic.com) so I have a basic understanding of how tone hole placement affects pitch, but why would the tone hole sizes matter? If I move the top of the tone hole up the body 1mm how does that compare to enlarging the diameter 1mm? It would effectively do the same thing right? t.
When tone holes are small relative to the bore, as for say recorder, then their size is quite relevant, affecting venting (hence pitch) a lot. A smaller hole lowers the pitch, even if the "northernmost" area of the hole's wall stays in the same location. After all, imagine if you reduced a normal size tone hole down to microscopic. It would stop acting as a tone hole at all.

However when tone holes are large relative to the bore, as with fltue or sax, the venting is already excellent, so enalrging the area has little effect.

But yes, if you increased the diameter by 2 mm, while leaving the location the same, that would be much the same as moving the tone hole 1 mm up the instrument. For the increased diameter, the slightly better venting might make the pitch slightly higher still.
 

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Distinguished Technician & SOTW Columnist. RIP, Yo
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17,204 Posts
The C# hole closest to the head on a flute can vary in size, at least from observation.
That's why, for some flutes, mainly older models, the C# is extraordinarily sharp. Grassi comes to mind.
That tone hole has many functions so significant compromises are made, with different parameters for different manufacturers.
 

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Distinguished Technician & SOTW Columnist. RIP, Yo
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If you have a choice, it is much better to make sharp notes flatter (using crescents) than to move or enlarge tone-holes to make flat notes sharper.
But this tone hole on a flute is a compromise for 8-9 different functions, and probably related to other design issues such as the head taper. The pitch of a particular note is not the only consideration.
These sorts of compromises abound in acoustic design of instruments.
 
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