Now you just open the Arduino editor, verify the sketch, plug in the USB, and upload. Here
's a video of what it should be like.
Of course there's plenty of room for modification and improvement. Some possibilities include:
* Adding a volume control like (potentiometer, or another photocell)
* Using a better speaker
* Making the code more efficient (fewer doubles)
* Taking advantage of the map function instead of mapping the calibration by hand
Feel free to suggest your own ideas, and have fun annoying people with your theremin.