There is growing interest in the field of augmented musical instruments, which extend traditional acoustic instruments using new sensors and actuators. Several designs use electromagnetic actuation to induce vibrations in the acoustic mechanism, manipulating the traditional sound of the in-strument without external speakers. This paper presents techniques and guidelines for the use of electromagnetic actuation in augmented instruments, including actuator design and selection, interfacing with the instrument, and cir-cuits for driving the actuators. The material in this pa-per forms the basis of the magnetic resonator piano, an electromagnetically-augmented acoustic grand piano now in its second design iteration. In addition to discussing applications to the piano, this paper aims to provide a toolbox to accelerate the design of new hybrid acoustic-electronic instruments.