The Lightning's Course by John Victor Peterson

It was only a robot, tiny, chubby, for all the universe like a Ganymedean monkey. It stood in the dark old mansion alone, stiff, immovable. Its pink, bewhiskered, rubberoid face seemed twisted with abject loneliness. Aye, it stood alone and lonely, as if awaiting the return of its master --

The song pulsed in a vibrant, ominous cadence through the streets of nightclad Certagarni, clashed against the glassite atmosphere -- retaining walls of the ancient Martian city, and penetrated faintly into a dimly lighted room of the Earth Embassy where the two earthmen sat smoking, listening.