Music isn't just for ears anymore. What ears have done for millions of years, oscilloscopes have done for about a hundred. Grab a thrift store keyboard, an electronic kid's toy, or any other electronic soundmaker and with a quick hack, turn those tunes into something your eyeballs can enjoy.

This is also a wonderful introduction, to waves, frequency, amplitude, harmonics, and many things under the physics sun. So, take that, you may just get in some learning, too. :)

What: Music You Can See
Concepts: sound, waves, energy
Time: ~ 20 minutes to make
Cost: cost of keyboard (ours was $10)
Materials:
- Keyboard (or grab a kid's piano toy, anything with an electrical speaker output)
- Two wires
- Alligator Clips
Tools:
- Screwdriver
- Wire Clippers
- Soldering Iron / Solder
- Oscilloscope (we use an old-fashioned one. You can also check with college physics departments as they usually have a lot of old ones, or check out this Instructable of turning your computer into one.)

Let's see some music!

Step 1: Opening Your Keyboard

Get to know your keyboard inside and out. Ours came from the thrift store for $10, and had approximately eleventy-billion screws on the back. Once those were removed, we could see all its insides. You can see the circuit boards, the keyboard inputs, and most importantly, the speaker it plays through and its two solder terminals.

Oh yeah, and old batteries from the 1990s which which look more toxic than the bad guys from Captain Planet. (We used the wall plug instead for power)

Step 2: Attach Two Wires to Speaker

Drill a hole in the side of your keyboard, and solder up two wires with gator clips. You are going to solder the other ends of each of these wires to the two speaker terminals in your keyboard. This will make it so any electrical signal that goes to the speaker will also go to our oscilloscope.

Thread the wires through the hole, so that we can close the keyboard back up and have them sticking out.

Step 3: Oscilloscope Time!

You're basically there! Grab/find/scavenge for an oscilloscope, and you'll find that it's worth it given the number of experiments that they can assist with. Hook up the two leads from one of the channels to the two gator clips coming out of your keyboard, and you're almost set.

The two main variables you'll mess with are the Time/Div variable (x-axis calibration) and the Volts/Div (y-axis calibration). This equates to the x-axis being time, and the y-axis being volts produced.

Nerd note: this wiki entry is great on oscilloscope history.

Trouble shooting: Depending on your oscilloscope and keyboard, it is possible that a low voltage from your oscilloscope might cause your keyboard to make noises without striking keys. If this is the case, first play with the settings to see if there's a work-around, and if not, you'll want to order a diodes to put in series with your keyboard-oscilloscope connection.

Step 4: See That Funky Music

Your music visualizer is ready to rock! There is much to see no matter what you hooked up, but if you have a full-on keyboard, here are a few investigations that are absolutely worth it.

Frequency: Try playing a note at a time, and going up the scale. You can see as the notes get higher, the waves get closer and closer together, and visa versa for going down the scale.
Amplitude: Turn the volume up and down on your keyboard, and see the effect on the waves. You can see volume's correlation with amplitude of the waves
Chords: Try playing one note, then another, and then both notes at the same time. The interference of the two energy signals aren't always what you'd expect. You can see a definite difference in "discordant" combinations, and those that sound more soothing.
Instrument Type: Beyond playing a main note, an instrument has many overtones, undertones, harmonicss, and more that give it a unique sound. If you have a keyboard, try flipping through sample instruments, and you can see how different the wave patterns are even when hitting the same key.

When you're all done a-rocking, check out this helpful tutorial on wavelengths, frequencies, etc. to see the physics at play.

And of course, always keep exploring.