Double a length of gutta percha tubing, say two yards long, and cut a
slit in the centre, where you insert one end of another piece of tubing,
of the same or a greater length.
In the two end openings put whistles, and make the whole air-tight.
Place the free end of the long piece around the nozzle of a bellows, and
on forcing the air from which into this novel instrument a double
succession of sounds can be produced. The whistles should be pitched
differently, and more than two can be used.