Digital music is typically created and edited within two distinct domains: audio space, and event space. Audio space represents music as samples (the musical equivalent of pixels), whereas event space represents music as notes and control changes (the musical equivalent of vectors). Many musically useful operations that are difficult or impossible in audio space are trivial in event space. For example, muting a track without cutting off notes that are already playing is easy in event space, but impossible in audio space. The Polymeter application operates entirely in event space, and generates no audio by itself. Polymeter outputs a stream of MIDI messages which must be routed to an output device capable of converting MIDI to audio.