The Planets, op. 32: VII. Neptune, the Mystic (for two pianos)

The original score for the planets was for two pianos, but this part - Neptune - was actually originally scored for organ "as Holst believed that the sound of the piano was too percussive for a world as mysterious and distant as Neptune". Nevertheless, he later published it as arrangement for two pianos. See https://en.wikipedia.org/wiki/The_Planets and https://imslp.org/wiki/The_Planets,_Op.32_(Holst,_Gustav)