You probably think I have too much time on my hands. This morning I took three cardboard tubes of different lengths: 14" (35cm), 27.5" (70cm) and 59.5" (151cm). They are all open at both ends. First I used them as didgeridoos by blowing a tasteful and prolonged raspberry down them. On the sound clip you hear the longest tube first, followed by the middle tube and then a trumpet-like note on the shortest. Each gives concert Bb but they are an octave apart. Using embouchure control it is possible to bend the note and alter the tone. I confess I am no didge player - the embouchure doesn't sit well with playing a clarinet - but I assure you that, in the right hands, the cardboard didge will sound quite acceptable. Just be sure, like any wind instrument, to give it a chance to dry after playing or you may find yourself with a biology experiment on your hands.The fourth sound on the clip is the middle tube, which came from a roll of wrapping paper, being overdubbed to simulate a group of players. Great for 'swarm-of-flies' sound effects!
Finally I hit the end of the largest tube with the soul of a slipper - a big insult to the tube, apparently. The knack is to cover the entire rim of the tube end as you strike, forcing the air inside to move. The sound is resonant but the last few hits are on the middle tube and this sound is less satisfactory. Because gripping the tube tends to inhibit its natural resonance, holding the tube vertically and dropping it onto the ground then quickly catching it gets the best percussive result.
The long tube came from a material shop, the short tube from a roll of cling-film.
If you can get hold of plastic tubing you will find it both more resilient and more resonant. Different lengths produce different pitches, regardless of the material used. One of the best instruments I have played was assembled at a camp by a friend of mine. It used thick blue gas pipe cut into different lengths and tied to a frame like some enormous set of pan-pipes. A pair of table tennis bats was used to hit the the pipe ends (because flip-flops weren't wide enough to cover the whole hole). Plastic tubes can be struck against the ground or other hard surface to create a pitched sound. In the picture two proprietary tubes (called boom whackers) are being struck against each other to produce a chord.





