Nice real working music instrument, with a beautiful sound.
Not every PLA print is as good as the other. I've printed it 3 times and 1 has a perfect sound, 1 has a good sound and the third one as no sound. I printed them in resp. red, black and glow in the dark PLA. Maybe its just a little thing why its not whistling, I don,t know.
Just try it.
Support Touching buildplate with 10% infill
After a cople of layers I lower the temperature to 45 degrees