We present a novel control algorithm for simulating an articulated character performing a given reference motion and its variations. The unique feature of our controller is its ability to make a long-horizon plan at every time step. Our algorithm overcomes the computational hurdle by applying modal analysis on a time-varying linear dynamic system. We exploit the properties of modal coordinates in two ways. First, we design separate control strate- gies for dynamically decoupled modes. Second, our controller only applies long-horizon planning on a subset of modes, largely reducing the size of the control problem. With this decoupled and reduced control system, the char- acter is able to execute the reference motion while reacting to unexpected perturbations and anticipating changes in the environment. We demonstrate our results by simulating a variety of reference motions, such as walking, squatting, jumping, and swinging.