Yet the Broadway musical persists, in its wholly impossible format, imposing eight big singing shows a week on its stars, which is, as any veteran will tell you, one of the most brutal workloads possible for a performer—and, when it occurs in long-running shows, mostly invisible as a personal triumph. The Phantom in the thirtieth year of “The Phantom of the Opera” might just as well be a phantom. For all that, theatre after theatre fills, leaving new shows searching for a landing spot.