In short… Do you have an Irish flute? How are things going with half-covers? The answer is no. We have bad sound!
On elliptical holes, we maintain the shape of the hole by reducing it with our finger. Like a recorder’s bottom holes
On the Irish flute we get a thin gap - but the air doesn’t like that! This is a thumb hole recorder effect.
Therefore, on my Irish flute in D, I want to make the lower hole E elliptical as well! Like the top one. It let me the better control on D# and the 2-nd octave (like recorder’s thumb hole), when it’s necessary.
On half of my flutes (quenas and quenillas), “half” covering the lowest hole creates a better note than normal - it seems to hit a particularly strong resonance in the tube which makes half-holing that note extra attractive. I normally make my flutes with big holes though (e.g. 11mm for the lowest hole), so even when half-holing there’s still a good size of opening left, and all the notes work well that way. Making some of the holes more elongated would likely do no harm though, and should have benefits on smaller-holed instruments, so I’ll try it. Having elliptical holes aligned with their longer length round the tube should also enable big holes that are easier to cover, making more powerful instruments practical for people with thinner fingers, though it may cause a bit more disruption to air flow within the tube - not a problem for the lower holes, but such a degradation in sound quality may add up to a significant amount if it’s done for all five of the full-tone holes.
