I want a whistle that sounds airy and warm. I want it to sound different from my Boehm flute that is bright and solid. What should my whistle be made of - brass or the Bakelite composite?
Try wood, or polymer, maybe?
This is far less a matter of material than that of design and manufacture. Since you are asking about those two materials, I assume you are planning to order a Burke. Go with the brass. If you sit on a composite one, it might break. The brass pro session d has a lovely round tone. Good luck.
If you’re making comparisons with a Boehm flute, I suppose you’re talking about … what? A low D? Presumably not a high D. If you tell us a bit more about what you want, whether you are indeed set on a Burke, and so on, we could perhaps help you more.
Well, I can tell you this much… when working with metals … Warmer = thinner walls. Or you can go slightly thicker walls with “ringier metals” such as stainless steel (pain in the arse to work with unless you’ve got awesome equipment)
The thicker the wall, the brighter the tone gets. basically just think about along the lines of a wind chimes… as the tube walls get thicker and thicker, the tubes vibrate less and less, therfore reverberate for a shorter and shorter length of time. Now put finger holes and a mouthpiece on all those different tubes and you get the same sort of effects. (Works with flutes too.. same analogy)
If I were going down that road I would start off with a thinner walled aluminum or brass to start with (they’re also cheap metals to start with) and see how you like it.
Working with composites… talk with another maker 
I’m not sure which thickness or pvc vs. composites will work out to give you a ‘warm’ sound.
It also has a lot to do with how the mouthpiece and blade angle is so I would imagine there is a lot that goes into the same manufacture and engineering of a flute, so there you have it!
Take care,
John
(Edited for typos and todays apparent eech inspediment and additional info)
If I can piggy-back on Jen’s question…What, if any, is the weight difference between for example Burke’s brass, aluminum and composite whistles of the same model, i.e., session pro?
Mike
The composite is like a feather. Next comes the aluminum. Followed by brass.
I have a Burke Brass Pro Session D w/Delrin head and it’s quite hefty. I like it that way.
SwtCaro
What is “hefty”? Louder? “Fatter” sound? - j
Jessie,
Thanks! I have some wrist and forearm weakness and it sounds like the composite would be the one for me. 
Mike
Nothing to do with sound, just weight, as in “s/he is pretty hefty, isn’t s/he?”
Yes, I meant it’s heavy, compared to other whistles I have (mostly pvc or cheapies). It’s not so heavy that you can’t play it, though. It seems quite solid.
SwtCaro
I have a Burke comp. D. I was astounded by its lightness at first. I have grown to like it a lot, but I would definitely avoid sitting on it. If it were an only child, so to speak, I’d prefer something metal.
i dropped my burke composites a few times, without damage.
i suppose i was lucky they’re not that fragile as i thought first.
on the other hand, a wooden whistle can crack, needs to be oiled,…
but all this are peanuts your looking at when you buy a whistle.
just pick the best sounding one when your in an exellent mood, and you made the best deal.
I’m a little scared of spending the $ on a brass. I tried a friends… it took more air to blow. After half an hour I was tired.
Do the composites take less air than the brass?
don’t worry about that jenny, half an hour is long for a beginner. they both require little air.
more important is choosing between narrow bore and session.
- the narrow bore is about the same boresize as a generation D(13.5mm).
-my brass session without the black tipped head is 14.2mm, or the same boresize as a generation C
-and my new composite D session is 15.2 mm.
the narrow bore takes a tinny bit less air than the session
If it were an only child it would be very brassy. I should know; I am one.
Hmmm…that explains a lot. As a third child I’m something of a composite.