So, yeah, I found my High D on the whistle a minute ago.
I was looking at sheet music for a tune called, “The Foggy Dew” - and it starts on what I was the 2nd octave F#… and calls for a D an octave higher than I thought I could play.
I’ve heard this D on high whistles before, but I never thought it would just pop out. I didn’t even know I’d played it until I was looking at the next stanza.
-Happypurringnoises-
So… yeah. I’ll be impressed if I can do that on my fife…
You mean D in the third octave, or D in the second octave?
The one in the 3rd octave that makes my windows flex.
I like to play American oldtime fiddle tunes, and there’s a great one called “Quince Dillon’s High D Tune”. It was originally played on fife, is now popular on fiddle, but it’s a great one for hitting that 3rd octave D on whistle! That’s the highest note I’ve attempted, myself!
I only have a couple whistles that do it faithfully, with musicality instead of screechy, and on pitch.
I just have to be in a big room to stand it. 
My supercheap sweetone can do it faithfully, and on pitch. Which suprises me, because the noise on it that passes for the low C-nat is absolutely… o.O icky.
I can’t get a listenable one with my Gens or my Soodlum, but the Susato and Sweetheart Pro D do it fine, especially the latter.