EverTune is a concept that ensures a resonating string will always play a specific note, ie. ‘be in tune’. It does this by supplying constant tension to the string. EverTune holds one end of the string and pulls on the string with constant tension. The frequency of a resonating string has only three variables: length, mass, and tension. Again, the note a string plays only depends on three data: the length of the string, the weight of the string, and the tension of the string. Strings drift out of tune primarily because the tension changes, their mass and length are more and less constant. EverTune, holding one end of the string, will pull with constant tension, and therefore the string will stay in tune until it wants to be changed.
EverTune’s first embodiment is for electric guitars. EverTune is a bridge for electric guitars. It is secured to the body of the guitar, and the ball end of the string passes through it, and over the EverTune saddle. Since EverTune is a technology that holds one end of one string, there are technically six EverTune modules in a six string guitar, one for each string; and they act completely independently. Thus, if a player breaks a string on a six string guitar, the five others are still in tune (theoretically they will be imperceptibly (to my ear anyway) flat due to the elongation of the neck that comes from the loss in tension on the neck from the string that broke—see note 1).
Each EverTune module holds one string. The magnitude of the constant tension supplied by an EverTune module can be set to any amount from 10 – 28 pounds. The tension of each EverTune module is set by a 2.5mm hex key that is supplied with EverTune and available at all hardware stores as well.
Since the tension of each EverTune module can be set by the player to any point in the range from 10 – 28 pounds, off frequency tunings such as 10 cents above and below standard 440, often used to match to off frequency samples, are part of the EverTune modules’ capabilities.
The first embodiment of EverTune creates constant tension via a spring set at a very special geometry and pulling on the bottom end of the saddle. Each EverTune module has its own spring. This spring, and spring housing, and bottom end of saddle are all embedded into the guitar and therefore invisible. The route cavity for the EverTune modules is similar to those for tremolo springs, about a half an inch longer, and a bit deeper.
The six EverTune modules are all housed in an EverTune faceplate. The faceplates and EverTune modules come in four standard colors: chrome, gold chrome, black chrome, and nickle. The faceplate is aluminum to be light weight and the EverTune saddle in each EverTune module is steel.
The EverTune modules are held to the faceplate by six intonation screws in the back of the faceplate. The intonation screws are hex head and fit the same 2.5mm hex key used for tuning. Turning an intonation screw right pulls its EverTune module, which includes the saddle, back thus lengthening the string length. Turning an intonation screw left pushes the module forward, thus shortening the string length.
The last component of the EverTune bridge are the six action screws which are screwed into the top of the faceplate. They are hex head set screws which use the same 2.5mm hex key that is used for tuning and intonation. The top of each EverTune module pushes up on the bottom of each action screw. Turning an action screw to the right makes it push its EverTune module farther down, lowering the string height. Turning an action screw to the left allows its EverTune module to rise higher, raising the string height.
The EverTune guitar bridge comes in three types: the F model is low to the deck and works with guitars such as the Fender® Stratocaster® and similar guitars with a low string to deck height, the T model is like the F model and works with guitars like the Fender® Telecaster where the bridge extends around the bridge pickup, the G model works with Gibson® Les Paul®s, 335s and similar guitars that use tune-o-matic bridges and have string to deck heights that are much higher than the F and T models.
In the case of guitars the neck could expand and contract enough over days or from a sudden decrease in tension, such as a string break, so that the length of the string between the nut and the saddle will change. Also the string could be corroded enough so as to lose enough mass to impact the tune. These are extreme cases, primarily the Length of the string between the nut/fret and the saddle is constant and the mass of the string is constant, and even when the length and the mass do change they will shift the tone by only a few cents.