Helmholtz Resonance Balloon Flute
The idea here described falls in the field of organology, or the science of musical instruments. A new wind instrument is described, the sound of which ranges over about one octave. Its merits are negligible cost, musical versatility, and potential popularity.
Obtain a plastic bottle of about 500 ml volume, in the hourglass shape typical of Coca-Cola®. The bottle's parts are described in US Patent 6695162 B1. Turn the bottle upside down. On the flat surface of one of its petaline feet, drill or melt a clean embouchure hole about 10mm in diameter. The edge of the hole closest to the bottle’s longitudinal axis is sharpened and slightly lifted, perhaps with a soldering iron. Remove the bottle’s cap. Pull the neck of a party balloon of about 100 ml volume (uninflated) over the full thread of the bottle’s neck. Fill the bottle and the balloon with water through the embouchure hole, leaving the upper 150 ml of the bottle’s chamber empty.
To play the instrument, hold the bottle’s waist in one hand, and blow over the embouchure hole to create a tone. Squeeze the balloon with the other hand, to vary the size of the chamber, and therefore the pitch. The physics are described by Helmholtz Resonance.