It’s every guitar player’s nightmare: you step onstage, strike your rock-god pose, triumphantly strum the first chord of a song–and discover that your guitar is out of tune.

A new line of instruments from Gibson Guitar now promises to banish this scenario to the dark ages with high-tech self-tuning technology built into the company’s flagship electric-guitar models.

The idea is drawing both kudos and criticism from guitar professionals and purists. On blogs and forums around the Web, some players call it an inexcusable crutch for sloppy players. Others, particularly those who use different tunings for different songs, say it could be a godsend.

Either way, the system is a sign that the music world’s digital transformation is reaching ever deeper, even into the rarefied circles of high-end analog instruments.

The Powertune system, to which Gibson announced exclusive distribution rights in January, was developed over the past 10 years largely by German engineer Chris Adams and Tronical, his small company based in Hamburg, Germany. Adams, a guitar player himself, says that he’d looked around for an automatic tuning system, found nothing that suited him, and simply decided to make one himself: “I thought, if we can fly to Mars, it must be possible to do something like this.”

Easier said than done, as it turned out. Adams says that it took years to develop a system that doesn’t affect the balance or sound of the guitar but is powerful enough to stand up to the stresses of string tension and playing.

The system begins with an additional set of pickups mounted underneath the strings that are used specifically for the tuning process. But unlike conventional pickups for electric guitars, which are magnetic, Adams uses piezoelectric pickups. These pickups are made from a material that creates an electric charge when stressed or pressured, such as by the sound waves coming from the guitar’s strings.

Typically used on acoustic instruments, piezoelectric pickups tend to focus on the single string above them rather than on bleed from neighboring strings. This allows them to isolate the sound of each string more exactly, Adams says.

The pickups are connected to digital signal-processing electronics mounted in the guitar body’s cavity. The pickups separately identify the frequency of each string.

Adams says that because the system is automatic, his company had to develop a tuning algorithm more sensitive than that of most external digital tuners. All guitar players are familiar with the waver of a tuner’s indicator needle even when a string is in tune: the waver results from the minor fluctuations in a string’s vibrations. A human tuning manually can easily ignore these fluctuations, but an automatic system must be programmed to discount them.

As the strings are played, the Powertune processor compares their actual frequencies with the desired notes and sends instructions–tighten the string this much, loosen the string by that much–to tuning pegs equipped with strong, tiny servo motors mounted on the back of the guitar’s head. Because onstage interference could potentially degrade a wireless signal, the system uses the strings themselves to send the signal.

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.”