In the wake of soprano Ana María Martínez’s notorious fall into the orchestra pit during Rusalka at Glyndebourne last weekend, Charlotte Higgins observes that “life on the operatic stage is increasingly perilous. No longer required simply to stand in the centre of the stage and exercise their lungs, opera singers are now expected to be multitalented actors, dancers, even acrobats; and to negotiate more and more elaborate sets for the entertainment of the audience.”