Traditional musical instruments have a direct connection between the way they are played or controlled and the properties of the sound produced. This connectedness has, in general, been lacking in computer-based musical instruments. We present a prop-based synthesis controller that uses a metaphor to create a connection between the control and the sound. Specific to granular synthesis, the metaphor is one of falling particles striking a surface to create a sound. The concept is extensible to other metaphors and other synthesis techniques. Keywords granular synthesis, metaphors, prop-based interface, computer music