I recently started on ornamentaion. I should have started shortly after I started playing whistle, but I didn’t know that at the time. Anyway, I’m working on cuts according to the instructions on Brother Steve’s site. It says to use the G finger to cut D, but when I do that in the second octave, I get a sound lower than D because there’s not enough breath pressure to make the higher sound. But if I increase breath pressure, the D shrieks. Anyone else have this problem? What is the solution? The obvious solution to me is just to use a different finger, but I didn’t know if this was correct or not. (If it matters, I am playing D with all fingers down.)
Have you tried by playing the high D with the first finger up? Just a suggestion 
Then you get a note lower than the D. Sounds like something between a C and a C#. I think you need all fingers down to cut from a higher note.
When I cut middle D, I usually have L1 closed and cut with R1, like this:
x x x | o x x (cut)
x x x | x x x
As you’ve found, if you cut with L1 vented, you actually sound a tap to c-natural instead of a cut from above. This is a hard, bubbly ornament and sometimes that’s the sound I want, so I go ahead and vent L1.
–James
P.S. Jen, I didn’t see your post before I posted. You are exactly right, and a lot less wordy than me as a bonus!
You can always do:
xxxxxo
xxxxxx (overblowing to get the octave jump)
It’s not illegal. 
So, how do you know when it’s ok to “bend the rules” and when it isn’t? Can you cut any note with whatever finger you like, as long as it sounds good?
It’s folk music; there aren’t any rules.
Seriously, the general rule is to cut with the G finger because it’s convenient – only one finger needs the muscle memory for cutting two or three notes – not because of the sound. In the cases that I can think of, I cut the middle D with the E finger; I’m sure I cut with the G or A finger in some cases. All that takes is a really brief burst of air to keep from octave dropping.
Yep, I was taught to vent the D and cut with the G (L-3)
Jen, it may depend on your instrument. In your first post it sounds as if this might be the case if applying more breath doesn’t solve the problem you describe. The solution is to find an alternative. Your whistle will show you these if you try different ways. Not all whistles finger the same.
Cutting with any of the notes above the note being cut can work in theory, but a different “flavor” will be got out of each one even though the cut is so brief as to be just a blip. You may prefer some cuts over others. I know a flute player who does almost all of his cutting by venting the topmost hole (the same one that plays B when it’s closed)! So, whatever works, but I think you need to like the result, too.
There are no general rules for this sort of thing, because it is pretty darn unimportant. For what it’s worth, Grey Larson says to use the E finger to cut D, LE McCullough’s examples are the G and the A(!) finger, and I couldn’t find anything in either specifically addressing the second octave. As I recall, Loretto Reid’s standard suggested high D ornament is to start with the first finger vented and then lift the top hand off altogether (though usually the context is to do it twice in a row to make a roll-like ornament).
If you do it correctly, it makes no significant musical difference what fingers you use to do it. The point is to break the D into two distinct notes, or emphasize its attack, and as long as you do that, very few people will care what finger you do it with (and they’ll probably fight viciously among themselves over what is the “right” answer).
Thanks, everyone! This has been helpful, and has given me the “freedom” do do what works for me and my whistle!
There are no rules about which finger to cut or tip with, use whatever finger or combination of fingers does the job on your whistle.
Good luck
John S