Lohengrin, which premiered in 1850 in Weimar, is the sixth of Richard Wagner’s thirteen operas, and the third he wrote (after Der fliegende Holländer and Tannhäuser) that is still regularly performed today. It stands very much at a crossroads in that it harks back to classical opera in some respects, but in others looks forward to the composer’s later music dramas by including leitmotifs and being essentially through-composed (although some distinct...