inherently acousmatic, as Lydia Goehr (1999) paraphrases, "the sound world is not a space into which we can enter; it is a world we treat at a distance". Style Acousmatic music may contain sounds that have recognizably musical sources, but may equally present recognizable sources that are beyond the bounds of traditional vocal and instrumental technology. We are as likely to hear the sounds of a bird, or of a factory as we are the sounds of a violin. The technology involved transcends the mere reproduction of sounds. Techniques of synthesis and sound processing are employed which may present us with sounds that are unfamiliar and that may defy clear source attribution. Acousmatic compositions may present us with familiar musical events: chords, melodies and rhythms which are easily reconcilable with other forms of music, but may equally present us with events which cannot be classified within such a traditional taxonomy. Performance practice Acousmatic compositions are sometimes presented to audiences in concert settings that are often indistinguishable from acoustic recitals, albeit without performers. In an acousmatic concert the sound component is produced using pre-recorded media, or generated in real-time using a computer. The sound material will then be distributed spatially, via multiple loudspeakers, using a practice known as "sound diffusion". The work is often diffused by the composer (if present) but the role of interpreter can also be assumed by another practitioner of the art. To provide a guideline for spatialisation of the work by an interpreter, many composers provide a diffusion score; in its simplest form this might be a graphic representation of the acousmatic work with indications for spatial manipulations, relative to a time-line. The acousmatic experience In acousmatic music, listeners are challenged to distinguish sounds, not based on their source, but by their sonic quality. As Pierre Schaeffer writes in his Treatise on Musical Objects "The concealment of the causes does not result from a technical imperfection, nor is it an occasional process of variation: it becomes a precondition, a deliberate placing-in-condition of the subject. It is toward it, then, that the question turns around; "what am I hearing?... What exactly are you hearing" -in the sense that one asks the subject to describe not the external references of the sound it perceives but the perception itself." That music is acousmatic is determined more by how it is listened to, than by whether it is being played from