Ah I see… horizonal vs vertical… here it’s most common to do it horizonally, with the mouthpiece facing towards the left, the bottom open end of the whistle facing towards the right.
I do the same things on middle D that I do on bottom D, true crans and what I call semi-crans.
From uilleann piping, the “rules” about crans are than any of three digits can be used: the lower-hand’s middle and index fingers, and the upper-hand’s ring finger; and they can be used in any order, but not the same digit twice in a row. A true cran has three cuts, a semi-cran or pseudo-roll, only two cuts.
So on bottom D or middle D you’ll see cut sequences in crans like:
xxx xox
xxx oxx
xxo xxx
or
xxo xxx
xxx oxx
xxx xox
or
xxx oxx
xxx xox
xxo xxx
(these diagrams are omitting the intervening D’s for brevity’s sake.)
All of these can be used on middle D too.
Now, for semi-crans /pseudo-rolls on D you can use any two of those three digits in any order, save using the same digit twice.
xxo xxx
xxx oxx
or
xxx oxx
xxo xxx
or
xxx xox
xxx oxx
or whatever. The actual cuts don’t matter, only the timing does. If you time it like a roll it comes out sounding like a roll, and blends perfectly with fiddlers doing a roll on that middle D.
What’s cool about these psuedo-rolls on middle D is that they sound different if you play the D open opposed to playing D closed. Open, both cuts are actually pitched around C# so technically are pats I suppose; playing D closed and the cuts come out as vague notes higher than the D.
Which leads to playing something that sounds like a true long roll on D: play any two of the cuts above (doesn’t matter which) and if you start the pseudo-roll with the D closed but open the D halfway through (by lifting the upper-hand index finger), the first cut comes out above the D, the second cut below the D, voila a true toll, done without any change in the cutting digits.
Really slowed down, with all the inteving notes notated, it could be diagrammed like this:
xxx xxx
xxx xox
xxx xxx
oxx xxx
oxx oxx
oxx xxx
Once again the exact digits used to do the cutting doesn’t matter to the effect; as long as you lift the top index finger in between the two cuts (shifting middle D from closed to open) so that one cut comes out above and the other cuts comes out below.