Unless a whistle is terribly out of tune, I would not cut or trim. Whistles are available in most all keys, though they are usually "spelled" in flats and not sharps-thus instead of D#, it's Eb. I also have Generation Eb & Bb whistles. The Bb was my very first whistle-given to me by a Bodhran playing pal in a Ceoli band I used to be in. I played along with pipes & pipe recordings. There are also pipes in keys other than Bb, which makes it necessary for other instrumentalists to play in other keys in order to join in. Also, the "Bluegrass" or "Traditional Music" keys of G & D & A are often not good for singers. Many singers prefer Ab, Eb, and Bb as their voice sounds better & works better or more smoothly in those keys--many church hymnals have more hymns in those keys.