This may have been covered in the past.
I found a way to reduce the “recordery” sound.
I know this works because I took it too far (of course) and destroyed one whistle, and got it just right with the second one.
Use a very sharp cutting device to remove the edge from the whistle’s blade. Remove about half a millimeter or less. You just want to blunt it a little. Then use a metal nail file to very gently smooth and round out the edge. However, if you like the sound you’ve already got, don’t screw with the nail file.
The whistle will still be loud and in tune. It won’t sound like an Overton, but it will be better. Keep in mind that the blade is not the one like on a Generation. The Susato blade is very delicate.
Mine (a Dublin model) seems to be easier to play at the high end, and definitely doesn’t screech at the high end.
I saw an interesting and related comment posted today…here it is:
"Mollenhauer, the German recorder maker (any wood from boxwood and fruitwoods to the hardest/oiliest like various rosewoods) recommends oiling of the blade, using a soft brush so as not to blunt it. "
Maybe blunting the blade would make the recorder sound less like a recorder?? Well, that’s what happended to my Susato.
I’ve only had one success story, (and one success story that I pushed until I went too far), so maybe I just got lucky. Take it for what it’s worth.
Tom.