For this reason, players typically tune between songs, rather than keeping the system active while they're playing--otherwise, the changing vibration of the strings being played and the electrical connection between the strings and metal frets could confuse the system.

The information sent to the tuning mechanism is encoded at a wavelength far above audible frequencies, so it does not interfere with the sound of the string, Adams says. Nor does the current flowing through the strings present any risk of electrocution: it's about the same level as that which flows through kid-safe model-train tracks.

The system is controlled by a "Master Control Knob" mounted like an ordinary control or volume knob on the instrument's body. Pulling it out activates the system; pushing it turns it off again, so the electronics aren't constantly trying to retune. A player can strum all six strings at once, and the process should have them in tune within a few seconds.

The electronics come with a handful of preprogrammed popular alternate tunings as well as the traditional one. They can also be used to tune the guitar to another instrument, such as a piano, or to store a player's own invented tunings.

This isn't the first, or the most advanced, self-tuning guitar system on the market. Over the past 20 years, a small Colorado company called TransPerformance has custom-built about 300 guitars, costing $3,000 and up for the electronics alone, for rock stars including Jimmy Page and Eddie Van Halen.

However, TransPerformance's system involves a complicated process of calibrating an onboard computer to link tuning settings to an individual guitar's unique characteristics, such as body shape and type of wood. This allows the TransPerformance system to change tunings more quickly and flexibly than does the Gibson system, but it also requires construction work on the guitar itself, which the Tronical components do not.

Whatever its technical merits, the $899 Gibson/Tronical system faces considerable skepticism from guitar purists, many of whom say that good guitar players ought to be able to tune their own instruments without automatic digital help. Some also feel that digital tuning systems can't ultimately counteract the often contrary nature of a guitar's organic materials.

"I think it's something that isn't necessary if you're a good musician," says Rick Kelly, a well-known custom-guitar maker at New York's Carmine Street Guitars. "I think there's something lost in the live experience when you lose the tuning aspect."

Nevertheless, it is true that many musicians carry as many as a dozen guitars with them to live shows, if they regularly play in alternate tunings. A retuning system eliminates that need, Adams says. "Many guitar players hate that they can't play their favorite instrument all the time," he says. "If you ask them, they're like tennis pros, who always want to use the same racket. This way they can play their favorite guitar all the time."