Do you think that the way you need to breathe for whistle is anything like the way you breathe for singing?
Also, how many octaves should I get out of the whistle? If I cover all the holes with my fingers, I get a D. If I blow a bit harder, I get a higher one. If I blow harder still, I get a third. If I blow really hard I get a really high D (and all the dogs for miles around come running)
Hitting the 4th octave ? Wild and daring man unveiled from his 2nd post ! 
Being from wimpland (y’know, them wogs past the Channel), I’m content with trying to keep one octave and a sixth consistent and clean, which I understood is not such an uncommon modesty…
And yeah, breathe with the diaphragm. As much you can…
I’ve sung in lots of choruses and groups for years… yes, I think breathing for the whistle is very similar. For both you have to fill up that diaphram and let out the air at a monitered, gradual rate. There’s actually a post down a little ways with some info on this, “Duh, stand up for more air!”
You should be able to get a full two octaves out of it; that’s really all you’ll need. Careful with the third+ octave stuff, you could bust an eardrum!
I wasn’t really aiming for it - I just got a bit frustrated, blew really hard and got interested by the result.
Try to take it really slow, and remember that you have to start somewhere.. you’re not gonna sound great immediatly. Just have fun with it! 
Actually, hitting four D’s is only three octaves, not four. How many octaves should you expect from a whistle? How many octaves do the pros use? Two, and maybe a few extra notes. Are the breath requirements for a whistle like those for singing? I think that it depends on the whistle you’re playing. If you play on a Shaw, you’re going to run out of breath quickly. If you are playing on an Oak, then you might have to exhale the remaining air, because you didn’t even use it, but now you’re out of breath, but you’re lungs aren’t empty (kind of like playing an oboe).
But I find that many non-musicians can’t maintain a second octave A on a whistle, because they don’t have the breath support.
I hope this answers you’re question.
JP
A lot like singing, BUT (you knew that was coming didn’t you? There’s a lot to be said for use of the toungue, and diaphram compression aiding you in getting the most out of a breath. Everything comes together quite nicely I think.There’s probably a post or two about both of those things somewhere in here… I’m sure of it!!!
Take care,
John
TaxmanUK should be inspected for development of weapons of mass destruction.
Geneva Convention formally states that a tin-whistle in 4th octave is to be considered a missile exceeding its allowed range 