In early conversations building guitars for Carlos Santana, Carlos insisted that Smith build him a guitar with a vibrato that stayed in tune. During the phone call, Paul Smith said "OK, I'll put a vibrato on it that won't go out of tune." After hanging up Paul remembers thinking, "How on earth am I going to do that?" And the quest began.
During the mid-1980's locking vibratos like the Floyd Rose and Kahler were state-of-the-art. Both used nut locks that required an Allen key to engage or disengage the locks. Additionally, the Floyd used locking saddles. These systems made string-changing a chore for artists. With the help of John Mann, Paul Smith set out to develop his currently patented PRS Tremolo system. It uses a six-screw pivot (like a Fender vibrato) but with each screw notched to accept the knife-edge of the bridge. The saddles sit within a walled top to eliminate any sideways movement that would throw your guitar out of tune. When Smith paired this design with his locking tuners, the system worked wonderfully, and to this day PRS guitars have a great reputation for tuning stability.