It is something of a miracle that a recording of Tristan und Isolde as accomplished as this one can emerge from a single concert performance. You soon become aware that the singers remain in one place and seem much less vulnerable to the vocal wear and tear that acting as well as singing Wagner can create. Nevertheless, this is not at all like a mere run-through. It is highly dramatic, tremendously well sustained and very well recorded, so that the mighty structure and the richly blended textures emerge with unusual clarity and immediacy.

Marek Janowski begins deceptively, the Act 1 Prelude warmly expressive but a little stately in its steady unfolding. Once the action starts, however, the music moves with decisive energy and a lithe, flowing articulation. Janowski occasionally forces the pace beyond what seems ideally natural; and, with brisk tempi obliging the singers to think in longer paragraphs, there’s a greater uniformity of dynamic levels than is sometimes possible. To my ears there is also a certain vibrancy, especially from Nina Stemme, though it never becomes a full-blown ‘wobble’. As is quite often the case, Isolde and Brangäne sound rather similar. This is perhaps Wagner’s fault as much as anyone’s – but it confirms that Stemme and Michelle Breedt are equally good.

Stemme’s turn from rage to radiance in Act 1 is matched by Stephen Gould’s transformation from stifled constraint to uninhibited forcefulness. Both singers negotiate the uncut early scenes in Act 2 with little sense of strain and Gould finds a contrasting gravity for his exchanges with King Marke – the excellent Kwangchul Youn. An abundance of uninhibited forcefulness is also needed from Gould in Act 3 and one possible complaint is that he doesn’t also manage to suggest the vulnerability which comes more easily to Tristans who have to act as well as sing. The sublime moment (‘Wie sie selig’) when Tristan imagines Isolde’s approach over the sea can be done with more tenderness than it is here. On the other hand, the final delirious exclamations are sung with superbly sustained musicianship and no shouting.

Is it possible that Stemme and Janowski were in two minds about the ending? The soprano is grandly impassioned in ‘Mild und leise’, unfurling a lustrous lyric line. The conductor opts for greater restraint, even though the spacious, uncluttered sound ensures that textural clarity in the orchestra is never at risk. Whether you’re convinced it works or not, it makes a striking conclusion to a memorable recording.