... guitars had fixed bridges, and if you wanted to play a note that was "between the frets", you had to bend the strings (or the guitar! :eek: ). So, the tremolo bridge was developed. This was originally intended to allow a guitar player to imitate the Hawaian sound that was usually only available with a laptop steel guitar. As the 50's music turned into Rockabilly and Rock'n'Roll, the trems were getting wanked around more aggressively, and tuning problems became an issue. Roller bridges, and roller nuts were tried as possible solutions, but it became apparent that the only way to keep the strings in tune was to lock them down solid at both the bridge and the nut. The most (arguably) successful design that took this approach was patented by Floyd Rose. There are now several variations and copies on the market, but they all have similar properties:

• The nut has some means of locking the strings so that they can't slip in the slots.
• Instead of tightening or loosening the strings from the tailpiece, the strings are locked into a moveable bridge that tilts with the trem bar.
• The setup involves a tricky balancing act. The string tension tries to pull the bridge so that the trem bar goes down toward the guitar body. The counter-springs pull the bridge the other way, trying to raise the trem bar.
• [u]Any[/u] change in string tension, due to aging, different gauge, different tuning, the phase of the moon, or the wind direction (LOL), often means that the bridge has to be adjusted to compensate.

The good news is that once you get it set up, a properly installed set of strings will stay in tune quite well.