Singers playing Singers playing Characters: Nila Parly watches the Copenhagen ‘Tristan’ take shape and talks to its director, Stig Andersen

From several of the corridors and rehearsal rooms in the backstage area of the new Opera in Copenhagen, built five years ago, there is a magnificent view of the port and the city. But in other parts of the building, the corridors where the artists come and go are uncannily reminiscent of a prison – not least in the area leading from the dressing rooms to the stage. Here, narrow corridors with an iron railing face a deep well, cutting through all five storeys of the building. A colossal white wall towers on the other side of the well. In the evenings, all the singers move along these artificially lit prison rows in the same direction, towards the stage, the fictitious universe in which they will be free of the confinements of the actual world for the hours to come.