A performed rhythm can sound 'mechanical', 'swinging', 'laid-back', 'rushing', etc. This is caused by playing some notes somewhat shorter and others longer in duration. But how does a listener perceive the timing of these rhythms and recognize it as being 'rushed' or 'swinging'? Why is a rhythm with a slightly shorter note not simply a different rhythm? How do rhythm and timing interact? This research shows that listeners do not perceive durations on a continuous scale. Instead, rhythmic categories are recognized that function as a reference relative to which the deviations in timing (or expressive character) can be appreciated.