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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.

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Credit: Gibson Guitar

Tagged: Computing, music, electronic gadgets, waves

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