I’m a pro classical flutist, although a bit out of shape in recent years due to caring for my small children. Playing Irish music has been a joy for me during this season, since it doesn’t require long practice sessions and agonizing over every detail of sound. I am however running into an intonation issue that I haven’t been able to solve.
I play a Casey Burns folk flute, the small-handed version, and I’m consistently sharp. I tend to lean sharp on classical flute too, but I’m able to get it under control on a modern flute. Meanwhile, my Irish flute is pulled waaaay out (making C# crazy flat), I’m lipping everything down, dropping my jaw - yet I still am higher than my session colleagues. The notes E and B are the biggest problems. I tried putting a bit of beeswax in those toneholes, but it deadened the sound too much. I haven’t messed with the head plug yet, mainly because I worry I’ll screw it up!
People seem to love these flutes, so I’m inclined to think it’s a “me” problem. Has anyone else run into this? Is it a classical thing? Would investing in a flute with a tuning slide help at all?
Lots of players on this forum with more experience than I have with a variety of makers, but I did own a Casey Burns folk flute that someone traded to me many years ago. And I, too, found that the intonation was tricky. Like yourself, it only played in pitch with the joint pulled pretty far out, and this seemed to cause other problems. He uses a pretty stout tenon on those, so pulling it way out created a substantial cavity in the bore, which was possibly contributing to the issues. But when I pulled the joint out to get the D note in tune, it messed with the intonation on the rest of the flute noticeably. I question how fixable any of this is, and if you really are loving playing Irish flute you might consider upgrading. If you are on a budget you’ll get a lot of decent suggestions here–there are some excellent flutes out there for reachable prices.
Many musicians I know would argue differently. I suppose it depends on how well you want to do it.
Thank you Geoffrey, this was tremendously helpful!
We don’t have to spend $30k on a flute and 5 hours a day in the practice room in order to audition for a session. 
If that is what you aspire to, perhaps not. But is that all there is when it comes to playing this music well?
Yes, it is a “you” problem, or more specifically a “your embouchure” problem. And I’m not being critical here. This is actually a very common problem with people coming from a classical/Boehm flute playing background. It all has to do with the angle at which you blow and how much coverage of the embouchure you employ.
Boehm flute players are typically trained to blow across the embouchure hole in such a way that the embouchure hole is not covered or shaded. In contrast, the typical way to play Irish flute involves directing the airflow more downward and shading the embouchure hole more. This allows you to achieve a different mix of harmonics, which people deem to be more traditional/authentic sounding, but it also lowers the pitch of the instrument due to the shading of the embouchure.
What this means is that to play a given pitch you don’t need the tuning slide to be extended as far, which sharpens the upper notes (B, C# etc) more than the lower ones, because the tuning slide has an uneven effect on the tuning of the flute’s notes (it changes the acoustic length of the bore proportionately more for upper notes than lower ones).
So you’re Burns flute has likely been made and tuned under the assumption that the Irish flute embouchure approach will be used to play it.
There is another issue going on with the C# tuning though, and that is that makers have to compromise the tuning of C# (all fingers off) and Cnatural (fingered oxx ooo), both of which are using that top tone hole to vent. The general consensus is that it is better to have the C# a bit flat in order to get the Cnat in tune and speaking better.
So C# is often a bit flat on Irish flutes, but your classically trained embouchure approach is causing you to have to extend the tuning slide a lot, which flattens C# further, and more than it flattens any other note on the flute.
Thanks Paddler! I suspected it was something like this, although I’ve been trying my best to aim my air down into the flute as much as possible instead of out and across like I do on Boehm. I’ll keep experimenting.
Yes, the E and A notes ARE veiled on simple-system flutes (smaller holes in order for fingers to reach D and E). B also can be veiled.
Keyed flutes vent E and A to a degree.
A Siccama flute has special keys to place the E and A holes in a better place for volume and quality.
Good to know! Thanks for your input.