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Spatial Properties
The spatial properties of sound have traditionally not been used in musical contexts. The only exceptions are the location effects of antiphonal ensembles of certain Renaissance and early Twentieth-Century musics, and the effect of the movement of the sound source found in certain drama-related works of the Nineteenth Century.
The spatial properties of sound play an important role in communicating the artistic message of recorded music. The roles of spatial properties of sound are many: it may be to enhance the effectiveness of a large or small musical idea; it may help to differentiate one sound source from another; it may be used for dramatic impact; it may be used to alter reality or to reinforce reality.
The number and types of roles that spatial location may play in the communication of a musical idea have yet to be exhausted or defined.
All of the components of the spatial properties are under very precise and independent control. All of the spatial properties have the capacity to be in, and to gradually change between, many dramatically different and fully audible states.
The spatial properties of sound that are of primary concern to recorded music (sound) are:
(1) the perceived stereo location of the sound source on the horizontal plane of the stereo array,
(2) the conceptualized distance of the sound source from the listener, and
(3) the perceived characteristics of the sound source's physical environment. The perceived elevation of a sound source is not consistently reproducible in widely used playback systems, and has not yet become a resource for artistic expression.
The three spatial properties are realized through stereophonic sound reproduction. The spatial attributes are related by the perceived relationships of location and distance cues of the sound sources in relation to the sound stage, and the relationships of the sound stage to the perceived performance environment of the recording.
Two-channel sound reproduction has become the standard for the recording industry, with monophonic capabilities still considered for adoption for AM broadcast and television sound. The two-channel array of stereo sound attempts to reproduce all spatial cues through two separate sound locations (loudspeakers), each with more-or-less independent content (channel). With the two channels, it is possible to create the illusion of sound location at a loudspeaker, in between the two loudspeakers, or slightly outside the boundaries of the loudspeaker array; location is limited to the area slightly beyond that covered by the stereo array, and to the horizontal plane. The characteristics of the sound source's environment and distance from the listener are affected in much more subtle ways by the stereo reproduction format.
A setting is created by the two-channel playback format for the recreation of a recorded or created performance (complete with spatial cues). The setting of the two-channel playback format is a conceptual (and physical) environment within which the recording will be reproduced more-or-less accurately.
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