In this paper, a scheduled controller is presented by the merging together of internal model-based control and linear parameter-varying control theory. The internal model is used to attenuate periodic disturbances and concepts from linear parameter-varying control theory are used to design the feedback gain that quadratically stabilizes the closed loop system during scheduling. An estimate of the frequency of the disturbance is used as the scheduling variable that updates the internal model. The order of the controller is kept low by making use of the separation principle and designing a reduced order observer for state feedback. A design example of a simple mass-spring-damper system demonstrates the effectiveness of the controller to cancel periodic disturbances with a time-varying frequency.