Sentence:  A biting , pithy parable of the all pervading hollowness of modern life , the piece has been set by Mlle Lagoon to a sumptuous score ( a <WSD>single</WSD> motif played over and over by four thousand French horns ) by existentialist hot-shot Jean-Paul Sartre . 
Meaning of the word marked with <WSD> tags:  being or characteristic of a single thing or person