"GUITARISTS TEND TO COME IN THREE SCHOOLS AS far as vibrato tailpieces, or “whammy bars,” are concerned: those who can’t live without them, those who can’t live with them, and those who tolerate them on their guitars, but rarely touch them—either for reasons of style, or for fear of spiraling out of tune. Love ’em or loathe ’em, vibrato tailpieces do change the sound of any guitar they’re mounted on, even when they’re not in use. If you do actually want to use one, however, and thereby indulge in the world of manual pitch-bend effects these ingenious contraptions can offer, it pays to know something about the form and function of the different types of vibrato systems that are available"
via guitarplayer.com