Sedi wrote:
Just checked my quenacho from Bolivia Mall again. Apart from the fact that it is slightly flat overall the second octave is in tune, maybe even a hair sharp. It has a cylindrical bore but super large holes.
I wonder how much of an effect the typical narrowing right at the end of the tube has on the tuning of the octaves. Even my aluminium quenacho has a rubber/plastic stopper at the end with a slightly narrower hole in it.
As near as I can tell, the real effect of that occlusion of the distal end of the flute is to keep the length of the bore a bit shorter. I've messed with adding them to various quena and quenacho and I couldn't perceive any other effect on the tuning apart from flattening the lowest note, allowing for a shorter bore. But I have not explored this with any systematic experiments so that's my impression from doing a handful of tests.
And when looking for a taper in the bore, it might not be an obvious, steep taper. Even a gradual taper might be an issue. And it's hard to measure both ends of the bore if it has the constriction at the opening of the foot.
So far I have never encountered a true cylindrical bore flute that plays in tune through both octaves without
some amount of lipping from the player. Some of the best examples of cylindrical flutes with good tuning are well made bansuri. The thin walls, larger finger holes and the proximity of the stopper to the embouchure hole all combine to make second octave tuning really good--so much so that it takes only the slightest amount of lipping to play the second octave in tune with the first, and sometimes no lipping is required. And flutes like the xiao and dizi tend to have oval holes, which helps intonation. The optimal hole location for the first and second octaves are different. For example, if you make a xiao and then place a hole right where it is perfect for that note to be in tune in the first octave, the second octave note will be a hair flat. The optimal location for the second octave note is a bit lower down the bore. Not a lot--maybe a millimeter in some cases. But if you make an oval hole that sort of straddles both hole locations you get the best of both worlds. Elongating the hole going South on the flute bore does not have significant impact on the first octave note, but it sharpens the second. Using this technique, plus some additional undercutting can make for a very accurately tuned xiao. But I've never had the second octave go sharper than the first. Not so when I make nan xiao, which are very like shakuhachi (being the forerunner of the shakuhachi). They have a tapered bore and the same issues with the sharp second octave can plague them.
This makes me think that sharpness of the second octave might be player compensation. Lipping up strongly with more forceful playing dynamics might do the trick.