Lesson 2-1-4 - Low F Natural
Low F natural is one of the nine half-holed notes in the standard 25 notes for a Key of D Whistle.
It's made by covering the top four holes completely, and then half-covering the fifth hole, leaving the last hole uncovered.
I find that squashing the right middle finger up against the index finger and tilting the nail slightly towards the ceiling while pressing down hard gives the most control while playing this note, although this is quite hard to master, and needs practice.
It's a difficult note, to be sure, but a very useful one, as F natural is the only note on D whistle that has to be half-holed to play a complete C scale.
As with all the half-holed notes, I'd recommend learning the full-holed notes first before trying them. There are fantastic whistle players out there who cannot play these notes with any degree of proficiency, and they still manage to play fine music.