A technique for reducing harmonic vibration in a multiplex multi-pump system. The technique includes establishing a lower bound of system specific vibration-related information such as via pressure variation or other vibration indicator. Establishing the lower bound may be achieved through simulation with the system or through an initial sampling period of pump operation. During this time, random perturbations through a subset of the pumps may be utilized to disrupt timing or phase of the subset. Thus, system vibration may randomly increase or decrease upon each perturbation. Regardless, with a sufficient number of sampled perturbations, the lower bound may be established. Therefore, actual controlled system operations may proceed, again employing random perturbations until operation of the system close to the known lower bound is substantially attained.