I have one Sindt Whistle, in "A," which Mr. Sindt made last September

It most respects it's far and away the best whistle I've ever played. It's just Fun, right away--it's a pleasure to make music on. It's easy blowing, it's in tune, it's got a sweet sound that you won't mistake for a flute or a recorder. My daughter, 14, plays the sax, and she noticed right away that it was really good sounding and fun when she played it.

The only drawback is the C nat requires half-holing. The cross fingered C nat is way out of tune. I've lately been trying to get better at half-holing, but it's not easy to do well--it's not too bad on slow tunes, but anything fast I just can't make it crisp enough. People do, so obviously it can be done, but I'm not sure it can be done by me. If I get better at it, then I'll be emailing Mr. Sindt again!

It may be worth experimenting a bit with different fingerings for Cnat, perhaps in combination with how you blow the note.

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My brain hurts

Just want to point out that crossfingering C natural and half-holing C natural aren't mutually exclusive.

It's standard on the pipes to do both simultaneously, and likewise I do that on whistles.

It's not half-holing in the sense of fingering C# and having to bring the note down a semitone, but rather fingering C natural and "uncurling" the upperhand index finger to "shade" C, when C natural is a long note and/or emphasised note.

This in on a Bass A whistle, but you can clearly see (and hear) the "uncurling" motion of the upperhand index finger

https://www.youtube.com/watch?v=rJm6BQ-Qxcg

Also I'm in the habit of blowing C natural a bit more softly, when necessary, to keep its pitch down.

That all being said I want whistles to play an in-tune C natural using oxx oox (the bottom hand can vary) and if crossfingered C natural is more than a tad sharp I might put tape on that hole.

I don't have any Sindts any more. I was able to compare a Sindt D to a Killarney D made a couple years ago, but not the current Killarney. My older and newer Killarneys play rather differently from each other.

(BTW on that video you can also see half-holing F natural (the note that would be F natural on a D whistle).

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Richard Cook
1978 Quinn uilleann pipes
1945 Starck Highland pipes
Goldie Low D whistle

I have indeed experimented with variants of the forked C natural. Best results are 0XX XX0 with some embouchure fussing, but the tone is kind of manky. I probably just need to practice some more.

Personally I stay with ordinary (at least for pipers) C natural fingerings on whistle such as

oxx oox

oxx xox

Breath and shading take care of a bit of sharpness, if there is any.

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Richard Cook
1978 Quinn uilleann pipes
1945 Starck Highland pipes
Goldie Low D whistle