Gustav Holst created a unique effect for the conclusion of his orchestral suite The Planets. He stipulated that the women’s chorus was “to be placed in an adjoining room, the door of which is to be left open until the last bar of the piece, when it is to be slowly and silently closed,” and that the final bar, performed by chorus alone, was “to be repeated until the sound is lost in the distance.”

Although familiar today, the effect thrilled audiences at the time. In her 1938 biography of her father, Imogen Holst recalls a 1918 performance by the London Symphony Orchestra: “But it was the end of Neptune that was unforgettable, with its hidden chorus of women’s voices growing fainter and fainter in the distance, until the imagination knew no difference between sound and silence.”

(Thanks, Ben.)