In Schaefferian theory, reduced listening is the attitude which consists in listening to the sound for its own sake, as a sound object by removing its real or supposed source and the meaning it may convey.
More precisely, it is the inversion of this twofold curiosity about causes and meaning (which treats sound as an intermediary allowing us to pursue other objects) in order to turn it back on to the sound itself. In reduced listening our listening intention targets the event which the sound object is itself (and not to which it refers) and the values which it carries in itself (and not the ones it suggests).
In "ordinary" listening the sound is always treated as a vehicle. Reduced listening is therefore an "anti-natural" process, which goes against all conditioning. The act of removing all our habitual references in listening is a voluntary and artificial act which allows us to clarify many phenomena implicit in our perception.
Thus, the name reduced listening refers to the notion of phenomenological reduction (Époché), because it consists to some extent of stripping the perception of sound of everything that is not "it itself" in order to hear only the sound, in its materiality, its substance, its perceivable dimensions.
Reduced listening and the sound object are thus correlates of each other; they define each other mutually and respectively as perceptual activity and object of perception. (Source - Michel Chion (1983). Guide des Objets Sonores. Eds. Buchet/Chastel, Paris. 1995 translation by John Dack/Christine North.)
Reduced listening is the most often used Schaefferian term in the English language.