Beyond the galloping finale of the overture (“Hi-Yo, Silver!”), Rossini’s epic of the founding of the Swiss Confederation in 1291 stands as one of the towering achievements of its era, in any medium. The world premiere at the Paris Opéra was a triumph, but the Wagnerian length of the score (some four hours of music) told against it. In our time, every revival is a special occasion—partly because the high-flying tenor part of Arnold Melchtal (a heroically inclined young Swiss torn between love and duty) has proved an ongoing headache to cast. In Juan Diego Flórez, Vienna has an aerialist who should soar to the heights with heroic ease. The distinguished baritone Christopher Maltman appears as Tell, the sharpshooter with the crossbow forced to take aim at an apple on his son’s head. With any luck, the cantilena Tell sings to the boy before releasing the arrow—“Sois immobile” (“Don’t move a muscle”)—will have listeners too caught up to breathe. —M.G.