Abstract: A piece of furniture has a frame and a part capable of rocking on the frame at a natural rocking frequency. A drive has a sensor for detecting movement of the part on the frame, a drive motor connected between the frame and the part for rocking the part on the frame, and a controller connected between the drive and sensor for rocking the part on the frame at the natural rocking frequency up to a predetermined maximum angular displacement of the part on the frame. The sensor detects angular movement, that is angular speed, angular position, and/or angular acceleration of the part on the frame. The controller has a response field and operates the drive in accordance therewith.