We tried two.
We cut them according to the directions, which you can view here, at Google Books. The flutes are on page 163.
The boys tried blowing into them, both on the end, and the side, but didn't manage to make a sound.
We did discover however, that pumpkin vines are hollow, which was interesting to the boys. They are also very prickly, which makes them dangerous musical instruments. And, they smell really bad - not at all like pumpkins.
While we were working with our pumpkin vines, my husband was carrying out his own set of sound experiments, answering the question, "What does it mean when you hear chomping sounds coming from your barbecue?"
The answer, he discovered is, "A small rodent is chewing up the inside of your barbecue cover, to use as material for building a nest inside of the grill."
This produced oohs, and awes from the the children, and an altogether different sound from me.
It's great to be a homeschooler.