Sentence:  On things that change as they move, Mr. Lelong writes, “when the composer <WSD>spatializes</WSD> a sound object — whether it is a chord, a motif or a rhythm — the sound object that is set in motion evolves, or to put it another way, the motion stimulated by the compositional process transforms the object, whereas previously works of spatial music merely give an impression of the same object moving unchanged through space.” 
Meaning of the word marked with <WSD> tags:  To localize sounds in physical space.