A musical or striking mechanism (1) for a timepiece or musical box, includes an energy source (6) delivering a mechanical torque and device for transmitting mechanical torque from the energy source to a wheel set for generating music or a striking wheel set (4). The mechanism also includes a wheel set governor (2) configured to regulate, around a reference speed value, the pivoting speed of the wheel set about a pivot axis, and including a break for braking the wheel set configured to return the pivoting speed thereof to the reference speed. The wheel set governor includes a system having an electric generator (16) whereof a rotor is mechanically connected to the energy source delivering the mechanical torque, and an electronic circuit for regulating the rotation speed of the generator.