For most of us, digitally capturing our six-string virtuosity involves plugging an axe into a guitar interface like Apogee's JAM and then launching some software on a laptop or mobile device. Researchers from Germany's Fraunhofer Institute for Surface Engineering and Thin Films are currently developing a somewhat neater, and potentially more accurate, solution that also holds the promise of replacing the humble guitar pickup. The guitar's tailpiece has been thinly coated with a contact material which is claimed to precisely capture complex playing movements in minute detail and convert them to digital control signals for onward processing.
The thin film coating on the tailpiece acts as a sensor to convert string tension into digital signals. Working with M3i Technologies, the researchers tested numerous coating parameters and contact materials before settling on a ten-micrometer coating of DiaForce - an amorphous carbon-based material that's also piezoresistive - which appeared to produce the best results, accurately capturing the subtle phrasing produced by the player (from gentle vibrato to stinging bends or lightning fast progressions) in something very near to real time.
"When the player changes the string tension, the pressure on the film changes," says Saskia Nina Biehl, head of the micro and sensor technology group. "This in turn leads to a change in resistance, which is measured by electrodes on the film."
The engineers are also looking to record the strength of a string vibration using the system - to digitally represent the strength of a player's stroke and the fading of the note, regardless of whether the player is using a pick or fingers.
Supplementing an earlier development where data from laser-based sensors are converted into digital representations of chord pitch and individual notes by specially-developed software, the project is now heading towards commercialization as a low-cost tension sensor for guitars and other stringed instruments.
It's also believed that, with some sensitivity tweaking, the technology could go on to completely replace pickups on electric guitars.
The following short video shows the string tension system in action:
