An electric machine coupled to rotating machinery includes a rotor and a stator, and the method of control of an electric machine and an electric machine control system. The method includes sensing one or more parameters indicative of one or more resonance conditions of the rotating machinery, and comparing the sensed parameter to a predetermined threshold to determine whether the rotating machinery is operating at the resonance condition. Where the rotating machinery is determined to be operating at the resonance condition, adjusting a magnetic field of one or both of the rotor and the stator to provide a predetermined torque to the rotating machine, to modulate the stiffness of the rotational machinery, and thereby move the resonance condition away from the current rotating machinery conditions.