As the sponge is squished more or less water lets more or less electricity pass through.
I made this to play with resistance and sound with Scratch and a sensor board...
You need to download the Scratch program and either make your own project or use this one that makes musical notes based on how much resistance there is in the sponge.
To combine Scratch and the sensor you'll also need to get a PICOboard along with the Scratch program.
You can use the Arduino with Scratch as well - look on the Scratch forums for a great program that connects Scratch and Arduinos
Lastly the sponge sensor might be great for circuit bending as well - then all your music making materials can be free and/or recycled
Step 1: Materials
Plastic cardboard - 1 sheet ( or scrap piece at least 5x10 inches) We need plastic because this is going to get wet. Save and recycle those political yard signs!
Telephone wire - 2 pieces about 10 inches each. This is also recycled: old computer cables. It has nice colors as well.
Sponges - 1 ( you'll cut it in half to conserve) I recycle or purchase the synthentic traditional kitchen - sized sponges ( run them through a dishwasher if you want to clean old sponges.
Brass fasteners - 4 of these.
Washers - 4 small washers that just the legs of Brass fasteners can fit through.
Aluminum (metal) flashing tape - about 10 inches. I bought a roll because I use this in all sorts of projects - its great. Find it at big box and small hardware stores.
Hole punch ( with long neck if you can find one)
Awl ( for punching starter holes )
metal ruler or yardstick (for guiding straigh cuts in plastic)
Start the other piece in the center leaving a gap. 1/4 - 1/2 inch seems to work well.
Try not to bend your hole punch handles. (like I did)
Then get the hole punch as near to the other end of the tape - try to get it near the center. This will depend on the length of the neck of your hole punch.
Put the other brass fastener through.
Wrap one ( circle the brass fastener a couple times) end of each around each of the brass fasteners.
Push the brass fasteners down again to keep the wire held tightly and bend the legs to hold them.
and you're ready to hook it up to the PICO board.
Go here to look at the Scratch project that shows how to make sponge music.