A Balloon Flute is made of PVC sprinkler pipe with balloons over each end, and a 3/8″ hole drilled into the middle. They are ridiculously simple the make. I made two today, and recorded some samples. One uses 2″ pipe, and the other 1″. The pitch is dependent on the flexibility of the balloons, which is variable by pressing on each end. Glissandi are possible, as are quick switches of pitch. They sound more like a whistle than a flute.
Bass balloon flute A2 25 cents sharp:
Soprano balloon flute B4 6 cents flat.