Here's how Keith Baxter makes his guitar go:
The guitar has only three strings. Rather than manipulating them on its neck, Baxter selects the chords he wants to play with a numeric keyboard attached to the side, which sends a command to his PC, via a USB cable, when he presses a button. He wrote software that matches each number to the string tensions corresponding to a given chord. The software routes these settings back to the guitar through a circuit board, and the motors instantly adjust the tension of the strings accordingly. In the future, he hopes to replace the setup with an onboard computer.
Like a regular electric guitar, this one plugs into an external amplifier. The guitar’s software allows Baxter to program different settings for different musical styles. He can use all rock chords one minute, then switch to slide guitar the next.
"No guitars were harmed in the creation of this project," Baxter jokes. He built the frame from plywood. It proved too flimsy at first, though—the neck bent as the motors pulled the strings tight, changing the tuning—so he added a one-inch steel pipe to the back to keep it stiff.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.