Method for controlling an ultrasonic handpiece of an ocular surgical system, such as a phacoemulsification system. First and second signal sources generate first and second drive signals. The first signal is at a first frequency and is used to drive a cutting tip of the handpiece with a first type of motion. The second signal is at a second frequency and is used to drive the cutting tip with a second type of motion. The different motions can be generated with different first and second frequencies. The first and second signals can be summed or combined and provided to a class D amplifier, the output of which includes multiple frequency components or multiple signals of different frequencies to drive the cutting tip in different directions at the same time, for example, with simultaneous longitudinal and torsional motions.