As a kid, electrical engineer Dan Sullivan mastered the guitar. His teenage sons, however, prefer mastering videogames. With a realistic instrument, Sullivan thought, all the time devoted to games like Rock Band could produce impressive musical proficiency. “You can show off playing guitar when you’re my age,” says Sullivan, now 58. “Being able to beat level 17 isn’t going to stay with you.”

Seven years ago, Sullivan left his cushy CTO job at a video-advertising company to develop JamStik, a digital six-string guitar. The compact neck has frets and strings like a real guitar but requires no tuning and doesn’t rely on push buttons like many digital models. Instead, small sensors embedded in the fret board track fingers illuminated by 52 infrared LEDs.

Because the sensors are spaced just a fraction of an inch apart, firmware interpolates the data to filter overlapping signals and determine the precise placement of each finger.