a metal scaffolding pole is a v cool thing to turn into an instrument. i like the weight, and the way it resonates.
a normal double-bass, for example, vibrates very differently, because the strings are coupled to the body in a certain way (it's the bridge what does it) and also because the wood responds in a certain way to the vibration.
but i wanted to try stringing a string along the whole length of a steel pipe (without a bridge) so that the string would be very strongly coupled to the pipe's longitudinal mode of vibration - i.e. so that the steel would transmit the sound through the action of the string "squashing" and "unsquashing" the pipe.
i asked some workmen if i could have one of their spare scaffolding poles, and they let me have a very nice one, about four feet long. it was dirty, of course, so i washed the thing in bleach before i did anything else. i strung it, devised a way of picking up the sound, and that was that - a lovely bassy-and-buzzy instrument.
the sound sample is three layers of scaffo (no effects). the buzziness of the instrument comes from the low "action" (i.e. the string lies very close to the pole) and also to some extent to the loose bridge.
you'll notice from the picture that there is actually a bridge. i needed to have one in order to lift the string a little way away from the pole; i did start off looking for steel pipes with a "lip" at the end so that the string wouldn't be flat against the pole, but that seems to be hard to find.
i found a really good piece of metal to serve as the bridge. it's flat and has a hole in the middle, and if you listen carefully in the sound sample you might be able to hear its effect - as i play it wobbles, adding a bit of a "phaser" effect to the sound.
as i said earlier, the resonance comes largely from the pipe's longitudinal vibration - so the pickup needed to be at one end of the pole, rather than attached to the middle. i solved this problem by putting a contact mic in a small steel box, and then literally standing the pole on the box. this gives really great coupling (i.e. it picks up plenty of the sound) and it's really quite a handy portable little thing.
i didn't find any suitable string (guitar/cello string not long enough, double bass string too expensive), so i tied together the three thick strings from a set of steel acoustic guitar strings. (the fisherman's knot is the best way to tie strings end-to-end.) i looped this new long string through the pipe and attached the two ends together using a machine head (the kind used in electric guitars - see picture).
i like the sound that is created by the wound steel guitar strings - bassy and buzzy.
some people have pointed out that if you don't want to tie three guitar strings together, you could try alternatives such as piano wire or 'weed whacker' line. i tried a second attempt using piano wire, and it's not suitable at all... too stiff for the purpose, i'm afraid.