Evertune
EverTune is an American company that produces the EverTune bridge, designed to keep guitar strings in tune.
Background
Stringed instruments, particularly guitars, have a tendency to get out of tune during playing, especially if strings are bent. In the late 1980s, Gibson developed a system called the Gibson Robot Guitar which used an onboard computer, motors, and a battery to keep the instrument in tune, but the system was complex and did not gain much marketplace acceptance, according to one report.Guitarist and engineering student Cosmos Lyles came up with a device to keep his guitar in tune, and with the help of engineer Paul Dowd produced a prototype of the EverTune bridge, which uses a spring and lever system that maintains string tension.
Invention
The EverTune bridge keeps a guitar in tune despite changes in tension. The mechanical device maintains a constant state of tension despite changes in temperature or humidity or the exertion of pressure on the string.On a guitar, the bridge has six springs and levers, one for each of a guitar's six strings, such that "when a string stretches or slips, the springs apply the opposing force necessary to compensate for the shift, thus maintaining the correct tension and tuning." In theory, the device can work with any stringed instrument, according to the inventors. The mechanism has been patented. A guitar with one installed is no longer tuned by turning the pegs at the end of the guitar's neck but rather with a screw on the bridge.