They’re called “slap tubes”…

…but the technical term is End-Struck Plosive Aerophones. If you’ve ever seen Blue Man Group, for instance, you’re already familiar with the DIY PVC pipe percussion instrument played by YouTuber snubbyj in this video. I built a one-octave set of these, once, and it took about an afternoon, and about $20 worth of stuff from the hardware store. They have a great sound—somewhere between a marimba and a guitar—and are dirt simple: Cut PVC pipe to various lengths, arrange as a piano keyboard, and slap the open ends of the pipes with foam paddles to play. [via Neatorama]

More:

• HOW TO – Make PVC instruments
• HOW TO – Build a PVC instrument