Somewhat of a newbie to the whistle - near 80 years a musician, mostly transverse flute. While noodling around, I tried rotating my finger around a tone hole - interesting effect. Is this a known technique in ornamentation? -Phil
Chris Norman uses it to some effect as well on the flute.
It comes from traditional playing in India, on the bansuri. The fingers are rolled around the tone holes to produce different effects. It’s a helpful method on a keyless flute especially but whistle, too, and can be done on whatever part of the hole is most comfortable to the player. So a “half hole” to produce the accidental can be moving the finger forward and uncovering the rear of the hole, or roll sideways either direction or slide backwards. Same for sliding or bending notes. (In Nicholson’s day it was described as a “glide.”)
Hope that helps!