I just got a flute I had ordered from Casey Burns. On the off-side of the embouchure there are three troughs gouged out. I thought perhaps these may be for draining excess body fluids (read dribble glass) but I’m sure there’s a better explanation. I queried Mr. Burns but got no reply. Any ideas what they’re for?
Thx,
djm
To allow the air to flow out faster, thus allowing you to play faster tunes!
Sorry, I don’t know enough about flutes to know if you are kidding or not (newbie). If you’re kidding, that’s okay. If you’re not kidding, then I don’t understand.
djm
Kidding. Sorry. 
Now a real answer:
It’s hard to say without looking at it, but sometimes people make cuts in headjoints to allow the air to flow more freely. The result is better projection, or louder sound, especially in the low octave.
For example, check the M&E page:
http://www.irishflutes.net/mef/Product_Descriptions.htm
and scroll down to where it has the “Split embouchure”
This could be something similar, but you say there are 3 cuts, so i don’t know. Maybe the easiest thing would be to ask the maker.
g
I believe they are there to increase volume and
give the flute more ‘edge.’
I think this is what you’re talking about (the headjoint on the top of the picture):
(hijacking an image from Casey’s site).
I think it’s likely to be done to improve power on the low octave. It may also allow you to blow harder on the first octave without “breaking” the sound.
But ask him! (and then let us know) 
it has to do with quicker respond time. Many makers do this type of cutaway, but in deferent ways.
But it’s done to improve the playability of the flute.
Yes, the top image is exactly what I have on mine. Casey calls this his session head, intended to let the flute cut through in group settings. I guess that’s what he means - for volume. Also, I get a very deep, dark tone in the first ocatve. Sounds great - very warm. Now if I could just hit that third octave …
Thx,
djm
I believe that Casey calls that his session head. It’s suppose to be designed to play louder, from what I understand.
Cheers,
Tony
The three grooves give you different tone. Blow over one groove for a Rudall tone, the second for a Pratten, and the third for a Nicholson. 
The session head is designed to give you more bang for your buck so you can get big tone without hyper-ventilating.
Cheers,
Aaron
Wow, three flutes in one!
Dana
It’s also known as the groovy head.
I don’t see it as an option on the price list or deferent models, does it cost extra?
No, I don’t think so. Casey includes it when he thinks
it will help the flute.
Jim is correct. I told Casey I’m a smoker, and the session head was his recommendation. I had previously purchased one of Ralph Sweet’s low-end sticks in maple and found it way too hard to blow, especially bottom D. The Burns flute is much easier to play.
Now all I need to do is quit smoking. No problem! 
Does anyone know enough about the physics of these things to explain how these grooves would actually make it easier to blow? My understanding is that you blow against the opposite side of the embouchure to create air disturbance to generate sound. How would these grooves increase volume?
Thx,
djm
I think it’s basically removing wood that isn’t needed for the sound production, so the air can flow more freely. Usually the cuts are more drastic, like the ones you see in the M&E flute i mentioned above, or http://drelinger.com/product.htm
But i guess even a small cut in the right place can help.
g
i think glauber is right. it may be that the airstream is “cut” or “split” by the far edge of the hole. some air travels in the hole and some continues on its merry way out over the hole. any (decent) cutaway on the far edge helps to reduce “friction” as it slightly increases the angle of the far edge and sharpens the cutting edge. i am guessing that ultimately it will reduce som “drag” to that part of the air column that is entering the flute so that it is free to travel with better velocity.
why the magical 3 grooves? i don’t know. maybe they are quicker at dispersing the unused air, seperating and “shooting” the air quickly out of the way. very groovy indeed.
Here’s another example of a cut (Clive Catterall’s “ordinary flute”):
(It’s hard to see from the picture, but he shaves off a cylindrical section from the far side of the blowhole. It appears whiter than the rest of the wood (which’s been stained).)
I think it is a misconception that air streams into the flute at the embochure hole. Take your flute, remove the body and produce a steady tone just using the flute head. Now feel the air with your other hand. You feel very little at the bottom (socket) of the flute, but a lot behind the embochure hole. The airstream produced bypasses the flute mostly, it gets caught at the edge and excites the air within the flute to vibrate. The vibrating column of air expands and compresses in the frequency of the tone produced, and leaves and enters the embochure hole as well as the bottom (vent-) hole(s) just a tiny amount, relativ to the amplitude/ loudness of the tone. Most of the air inside the flute is not going anywhere, just vibrating. But most if not all the air coming out the mouth bypasses the flute at the embochure hole. So to improve airodynamics at the outside of the flute makes sense.
hope that this makes sense.
Hans, this falls in line with my understanding. The pressure waves inside the air column inside the flute’s cylinder hit the difference in room pressure at the open tone holes and most of their energy is deflected back up the column to affect the air stream over the blowhole. So what you’re saying is that the grooves on the embouchure increase the air stream velocity on the outward side, which increases the amount of air being vibrated out into the room, which equates to greater volume of sound to listeners.
Thx everybody,
djm