VICTORIA, Malta—The tiny island of Gozo, population about 37,000, has one hospital and oneMcDonald’s. But it has twoopera houses.

Astra and Aurora are owned by rival band clubs that both trace their founding to 1863. For over a century they have been one-upping each other in everything from musical performances to feast-day celebrations. Once, when Aurora heard rumors that Astra planned to bring a horse onstage during a performance of “Aida,” the competing house—which was presenting its own “Aida”—secretly casttwo horses.