Telescopic Horn

very easy and efficiante telecopic horn playable as didgeridoo or alpen horn....

for a horn from 0,15 to around 3 meter long
make a roll of plastic shock (thermoformable)
thickness: 0,5 mm
high 15 to 17 cm
lengh: around 10 meters
a rubber band

Roll it with a inner diameter of 5 cm
put the rubber around it to contain the plastic.

Pull the inner corner while maintaining the out part of the roll.