A new device allows musicians to control sound effects with a wave of the hand. While electric guitarists typically control distortion effects with an array of foot pedals, the HotHand device, made by Source Audio, translates their gestures into the wah, phaser, and flanger effects that are popular for electric sound. A musician can wear the device as a ring, affix it to his or her head or torso, or allow someone else--such as the band's vocalist--to use it to control effects. A wireless option leaves the wearer free to roam the stage.

"If you're going to use something like this, it's a visual thing," says James "Fuzz" Sangiovanni, who demonstrates HotHand for Source Audio's instructional videos and is the lead guitarist for Connecticut-based indie rock band Rolla. The device, he says, allows him to make controlling the effects an expressive part of a show.

HotHand uses a MEMS accelerometer to detect motion. Information from the accelerometer is sent to a chip that converts it into a digital signal, processes the signal according to the settings selected on the effects box, and then converts it back into an analog signal that is sent to the musician's amp. The way different gestures affect the sound was decided subjectively, says Roger Smith, cofounder of Source Audio. "It's like tasting wine," he says.

There are two effects boxes available for HotHand: a wah filter and a phaser/flanger. Musicians can set the accelerometer to varying degrees of sensitivity, selecting "pick" to make the device sensitive to the subtle hand movements of picking a guitar, "strum" for medium sensitivity, or "flail" to filter out everything except wild arm movements. The device can be used with any electric instrument, including keyboard, bass, or electric violin.

The idea to use an accelerometer to control effects came from Jesse Remingnanti, cofounder of Source Audio. An employee of Analog Devices until he left to start Source Audio, Remingnanti had the idea to combine three elements familiar to him: the accelerometers that Analog Devices made, the sound-processing chips that he'd worked on there, and the music he played. (Many of HotHand's components are made by Analog Devices.)

Joe Paradiso, director of the Responsive Environments Group at the MIT Media Lab, says that he thinks it's natural to incorporate movement sensors into the design of musical devices. "I think movement and sound are intimately related," he says. "When you hear music, it makes you want to move."

As MEMS technology becomes less expensive, Paradiso says he expects to see it in more musical products and academic projects. He points to the use of an accelerometer to control an effect in the popular game Guitar Hero, as well as to more-experimental projects, such as his group's project to use sensors to convert dancers' movements into music.

Daniela Marquez, who plays keyboards and trombone with the Boston-based funk band the Koop, says that audiences are fascinated by the glowing blue HotHand ring she wears during shows, particularly when they realize it controls some of the sound. "It's really cool to have another dimension you can use to captivate your audience," she says.