My Dad and I went to the store and bought, 11/2 inches PVC Pipes and we bought one piece of plywood.
My Dad cut the pipes to the length that was needed.
For the wood my Dad drilled 11/2 inch holes for the pipes. I spray painted the boards green, I wrapped the pipes with black tape to hold them in place I also wrapped the top of the pipes so the balloons wouldn’t rip.
To make the sound, I tap the balloons or pat them with my hands or with sticks.
I can change the dynamics by hitting it harder to make a loud sound. So if I hit it lightly to make a soft sound. To make the pitch change I have to hit the longer tube to make a low sound. To make a high sound I hit the shorter tube. I thought that the timbre is tuneful.