Tuning wrench

A tuning wrench (also called a tuning lever or tuning hammer) is a specialized socket wrench used to tune string instruments such as the piano, harp, and hammer dulcimer, that have strings wrapped around tuning pins. Other string instruments do not require a tuning wrench because their tuning pins or pegs come with handles (as with the violin), or geared tuning machines (as with the guitar or banjo).