Lohengrin of 1850 is the sixth of Richard Wagner’s thirteen operas, and the third he wrote (after Der fliegende Holländer and Tannhäuser) to be regularly performed still. 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 leitmotives and being essentially through-composed (although a few distinct arias are to be found within it). It is also the...