Abstract: A bridge assembly having a saddle plate, a tremolo block, and a bushing extending through the saddle plate and tremolo block. The bushing has an internal bore, and an engagement member extends through the bushing and is partially disposed in the internal bore. A tremolo arm has an engagement section with a flat engagement surface that defines a plane substantially parallel to a longitudinal axis of the engagement section. The engagement member is perpendicular to and laterally disposed from the internal bore's longitudinal axis. The engagement member frictionally engages the flat engagement surface when the engagement section is disposed in the internal bore. The tremolo arm's engagement section rotates with the busing as a unit relative to the tremolo block.

Abstract: A module for removable insertion into a body of an instrument having longitudinal strings, the body defining a transverse cavity extending from a lateral edge. The module includes a base configured to engage the cavity as the module travels along an axis of movement into the cavity. A first ball plunger contact is configured to conductively engage a corresponding first contact plate affixed to the body when the module reaches at a first point in movement along the axis and to remain engaged as the module moves into cavity along the axis of movement. A second ball plunger is configured to conductively engage a corresponding second contact plate affixed to the body when the module reaches a second point displaced inwardly from the first point in movement along the axis and to remain engaged as the module continues to move into cavity along the axis of movement.