Lengths of plastic tubing, ranging from about 6 feet to a foot can be put into a simple frame and hit at the top end to create very interesting sounds; using homemade bats or table tennis bats. I am talking about the blue, wide diameter pipes, ( 10" ?), that the water companies use underground; they will often give off cuts away to schools or charities. It's a simple idea but the sound created is a loud,hollow, echoed POP and quite addictive to kids and adults. Good luck.