Imagine a performance of Swan Lake in which Odette waves her arms up and down and runs in circles while a puzzled Prince Siegfried looks on, scratching his head. Eventually the exasperated ballerina simply stops, turns to him, and says, “Don't you get it?—I’m supposed to be a swan!” Few rules in any art form are more stringent than the rule in classical ballet that dancers can't talk. Long ago I saw at Covent Garden a performance of Kenneth MacMillan's ballet The Song of the Earth, in which Anthony Dowell made a megaphone of his hands in front of his wide-open mouth, as if he were going to shout something. As it turned out it was only a mime of a scream, but the strong implication of taboo breaking made that one of the most memorable moments in the whole genre of ballet, comparable to the end of Balanchine's Sonnambula, when the woman picks up the man and carries him offstage.

But if speech and song are forbidden to dancers, dance is perfectly acceptable for operatic singers, even in the case of singers constitutionally unable to dance. A happy soprano surprised by an expensive present from her lover might skip with joy; a cunning mezzo might raise her skirt and clack her castanets; a dying basso in his dragon suit might even get a little choreography for his final spasms. Often in opera the dancing is quite unobtrusively integrated into the drama, as in the ballroom scenes in La traviata and Eugene Onegin. But what interests me here is the other kind of operatic ballet, in which there is a certain strain or even fracture about the copresence of dancing and singing; in which the conventions of opera and the conventions of ballet jostle uncomfortably; in which the composer may have been forced to provide a ballet against his will; in which there is little sense of Gesamtkunstwerk but a strong sense of Zerstückelnkunstwerk (shattered work of art).

The great master of the inconsequential ballet was of course Meyerbeer, who thought it a fine thing to provide, in Le prophète (1849), a little relief for the bloodthirsty, war-torn Anabaptists in the form of a delicious ballet in which provisions sellers on ice skates—simulated with those newfangled contrivances, roller skates—take a break from their capitalist enterprise by dancing.