When listening to whistle music from “Scotland” and music to the ‘North of Ireland’, such as by “Altan”, the music seems to be played in “C-major” yet very little sheet music exist for it. Anyone know any sources?
BTW. I bought my Generation C just because I love to play “Red is the Rose”. I was never able to find music for the “D” that would play that tune. With the “C”, it just flows out… (A nice excuse for WhoA too!) 
Find the music in D and play along on a C whistle. It will work.
For the most part that playing along seems to work. I was just hoping to find some like “Red is the Rose” that works on a “C” but is just a little off on the “D”. To handle the problem with the “D” and that tune, I have found music that tries “faking” the c below the lower d or another that did an octave jump. Neither worked well and I needed an excuse to buy another whistle or two.