I used a plastic coffee can for the sounding tube by removing the lid and cutting a large hole in the bottom. The vacuum form of the can's bottom gives a perfect template for cutting a nice, large round hole while leaving a lip around the bottom edge.
Cut a latex glove into a section large enough to cover the top of the can. Secure the membrane to the top of the can with a rubber band. Pull the edges of the membrane until the membrane surface is taut and even. Trim away the excess if you want to be neat... =)
Otherwise known as a cheap auxilary speaker like you can buy at Radio Snack or find at a garage sale that has a mono jack. Remove the top cover of the speaker, then superglue the bottom lip of the coffee can assembly to the speaker edge.
Make adjustments in the coat hanger holder until the pointer beam lines up nicely with the mirror. Placing the speaker on top of the wire base works wonders. Now plug the mono jack into your PC output, cue up your favorite tunes, and get ready for the show!
It's really fascinating as you can see the shapes made by solo instrumnts, and how they grow or shrink as the not is changed. You'll also get some nice linear and circular revolving patterns depending upon the music and instruments. The coolest thing about this is that you can project this onto a house, billboard, gymnasium cieling, or just about anything you can think of. Theoretically, even a low lying cloud base (I'm looking forward to a day when I can try that!). See the video for a great example of the lightshow functioning. Have fun, and suggestions or questions are welcome!