I designed a small whistle as a starting point for a playable ocarina. My plan is to make something that sounds decent as a closed vessel, then drill finger holes starting with the lowest notes. If all goes well and I can get it tuned, I'll measure the holes and add them to the model.

Starting with a 2cm cube I added rounded corners with the built in minkowski function and then added "mouthpiece" using a fillet function I found here:
https://github.com/clothbot/ClothBotCreations/blob/master/utilities/fillet.scad

Next I hollowed it out and added a fipple using the technique of TLAR (that looks about right) and was a bit surprised that it actually played a note (sort of). Some adjustments may be needed here...

Eventually I'll make it a bit larger, this was just a quick test print. I'm also trying out some different print orientations. I put it 45deg on edge because that first layer is usually pretty ugly and PLA printers seems to handle that much overhand fine without support. I've also included the STL w/o support in case you'd like to do that yourself.

Thanks for looking!
Bob M

Update: multiple changes to the .scad file. See github for a complete history: https://github.com/bobm123/maker

I rendered a larger one with interior volume of about 65 x 45 x 25 mm and included a couple of .stl with support options I was playing with. According to my chromatic tuner, print plays a slightly flat C#. Next I'll see if I can make it into an ocarina.

I did my first print from the STL file with support, slices set for .25mm layer height, 15% fill. My print time was about 45 min.

Same print settings used for the larger version oriented on its side. Print time was about 2 1/2 hours.

To generate a whistle at a different size, open whistle.scad and modify the length, width and height parameters. You can also try one of my two attempts at generating support by removing comments at line 23, 24 or 25. If you go for the unsupported version, you'll probably have to add some with your slicer. I gave up with the auto generated supports as they kept messing up the interior. That's why the other two versions. If you try the 90deg orientation be careful with the height or you might run into trouble making the bridges for the top of the print.