What is a good exercise to learn them? I’m finding them difficult to execute. Thanks!
Robin
Cranning is pretty much synonimous with piping, though it can be used in whistle/flute playing. Primarily, crans are used on the bottom E and D notes. To play an E cran, sound the E note, and then cut with A-F-G. To cran the bottom D, you would first sound the D, then cut with G-F-A.
It’s a tough ornament, kinda like a roll, rolled back on itself. Take the time to practice it slowly, and you’ll have it down before ya know it.
At least, that’s what the NPU videos keep telling me! LOL
B~
OK, I think that link tells me exactly what I’m up against! I guess I’ll just have to sound like a drowning whale for a while until I master this one… 
Robin
Keep practising them separately and very slowly, and only speed them up very gradually. If you get into the habit of playing them “more or less OK” in tunes at normal speed, you will develop the bad habit and it will become even harder to play them really cleanly
I think you can play the whistle quite nicely without them. Out with the clutter!
I’ve been listening to my John Skelton “A Few Tunes” tape quite a bit and he almost always crans high D’s when they come along, but not low D’s. I do like the sound of the high D crans. Low D crans do tend to sound cluttered/mushy on some whistles.
I know in theory how they’re done but still haven’t got the hang of them…
-brett