A bracket for mounting a tuning device on a headstock of a string instrument and a bracket-mountable tuning device are disclosed. A primary arm with a plate attaches to a spring arm with a clamping arm by a releasable ratchet engagement. The clamping arm is reciprocable to the plate. A tuner attaches in a rotatable engagement to the plate opposite a mounting surface. An instrument headstock can be positioned between the plate mounting surface and clamping arm and the clamping arm moved toward the plate to a clamping position with the headstock trapped therebetween with substantially constant pressure on the headstock. The tuner is substantially hidden from the front view of the headstock. The clamping arm is maintained in the clamping position by the ratchet engagement until the ratchet engagement is released.