Twentieth-century composers experimented not only with the organization of pitch structures, but also with rhythmic and metrical structures. Yet research exploring these latter elements is limited in scope. My paper aims to expand theories of rhythm and meter to explore the relationship between these musical elements and temporality in unmetered music. Without a steady pulse and metrical structure demarcating time and  providing a framework within which the listener can place rhythmic events, ‘unmetered’ music creates an environment in which composers can manipulate the listener’s sense of time passing through the organization of musical events in time.
I identify a set of mechanisms used by composers which contribute to fluctuations in the listener’s perceived passage of time. These mechanisms are grounded in psychological studies addressing influences on the perception of time passing through an examination of external (experienced events) and internal (directed attention) forces. Through a set of analytical vignettes focusing on the work of George Crumb, I show how the repetition of certain rhythmic motives, the presence of competing pulse streams (Roeder 1994;2001) and the occurrence of metrical emergence and dissolution (Horlacher 1995) can be used to manipulate the perceived passage of time within the music. By developing a theoretical framework that emphasizes the interaction between rhythmic and metrical elements and our perceptual experience of time, I demonstrate how composers can and do systematically manipulate time in unmetered music.