Cheers, it’s an instrument called ‘the wires’ that was built by Alan Lamb.
You can use all sorts of materials. I think I remember he’s been using high-tensile steel wire. It’s not fencing wire.
Another consideration is resonance. In the video above I recorded it with a polystyrene box wedged in one end. Lamb introduced me to contact mics and I’ve experimented with smaller spans, like this slippery slide:
You know when you find a useful resonant frequency 
Thinking of resonance, fences are great. Particularly those with palings all the same length, especially if they’re made from a resonant metal like aluminum. Similarly with bars that are all the same length, like playground equipment.
https://youtu.be/yLLLHYJOokc