Alien symphony conductor from Venus on the Half Shell by fictional science fiction author Kilgore Trout. A recurring character invented by Kurt Vonnegut, fellow author Philip José Farmer thought it'd be fun to write one of Trout's novels that only existed as a title and short excerpt in God Bless You, Mr. Rosewater (1965).
It was first published in the December 1974 issue of Fantasy & Science Fiction:
Simon knew something about towers like this one, which was why he was delighted to see it. Interstellar voyagers to distant galaxies had reported finding such towers on every inhabited planet of these systems. There were however, none on the planets of Earth’s galaxy. Nobody knew why, though many resented this slight.
Of the six million towers so far reported by Earth tourists, all had been just like this one. The natives of various planets had tried everything from diamond-tipped drills to laser beams to hydrogen bombs without scratching the mysterious metal. The buildings were hollow. A hammer could make one ring like a gong. There was even one planet which had a symphony orchestra which played only one instrument, the tower. The musicians stood on scaffolds built at various levels along the tower and struck it with hammers, the size and layout of the rooms within determining the notes evoked. The conductor stood on a platform a mile high and half a mile away and used two flags to wigwag his directions.
The highest point of music in the history of this planet occurred when a conductor, Ruboklngshep, fell off the platform. The orchestra, in trying to follow the wildly waving flags during his descent, produced six bars of the most exquisite music ever to be created, though some critics have disparaged the final three notes. Art, like science, sometimes gets its best results by accident.