A keyboard percussion instrument (100) generates sounds when keys (130) or other such members are struck. A movable damper bar (140) is brought into contact with the keys to artistically shorten their ringing duration. When pressed, a pedal (145) removes the damper bar from contact with the keys. When the pedal is released, a spring (1010) urges the damper bar into contact with the keys. The damper bar is supported by a pair of arms (165) that pivot about pivot points (800) at the ends of movable posts (520) that extend from a pair of pivot height adjusting mechanisms (175). Each pivot height adjusting mechanism has two adjusting screws. A first screw (510) urges a post to move up or down and a second screw (565) fixes the post in position when tightened. Adjusting the heights of the pivot points provides control over the damping of key vibrations.