Along the lines of the clay whistles you might also want to look at making
clay "Octarinas". I did this project with 7th graders a few years back which
much interest and success. The kids liked the idea of making an instrument
that could play a few distinct notes.
I too, studied some books on primitive instrument making and had a few
conversations with our music dept. But, the most valuable thing was just
looking at an authentic octarina a friend had. The basic body of the
octarina is hollowed out of a small lump of clay with a wire loop tool. The
opening for the mouthpiece was the trickiest part. I gave the students some
diagrams and cut a way views to help them understand the principle of the
air being channeled across an opening and striking a sharp edge to make the
sound. Then had them observe some demonstrations. Most were successful in
making the octarina actually work.
It took about 4-5 hour long periods for the basic construction, we raised
them on star stilts for glaze firing.
It was fun to make a functional project that was also aesthetically
pleasing. Great opportunities for discussion about form and function, art
history, etc. Plus our music students really loved them!