At the end of the day – which we have now reached for this live Hong Kong concert Ring cycle assembled over four years – this project’s main achievement may well prove to be the maturing of orchestra, conductor and recording team in performing Wagner’s music. Each instalment has represented a measurable advance on the last – and the orchestral brass, in particular, may feel proud of their work here. There have been objections to Naxos’s varying cast (though we have had a single Wotan, Mime and Erda) but this is not a stage cycle and these changes have helped keep the project in touch with today’s upcoming voices.

Of this recording’s ‘newcomers’, Gun Brit Barkmin (her debut in the role) brings imagination and flair. It’s quite a ‘white’ voice and not a huge one but she’s a committed projector of the drama. This cannot (quite) compensate in the sections of the score that are, at least for now, just too weighty for her, especially, in Act 2, the oath on the spear and the later outburst of grief which provokes Hagen’s offer of revenge. Daniel Brenna’s voice, again not heavy but well focused, certainly records comfortably and he is always fully in touch with the dramatic requirements. Eric Halfvarson’s Hagen, more experienced than this pair, is both vicious and frightening (as opposed to just plain ‘black’) of voice but occasionally sounds not in 100 per cent of health. Shenyang’s impeccably voiced Gunther sounds like he has just emerged from language school, so carefully received is his pronunciation. Amanda Majeski’s Gutrune is similarly noble without much dramatic impact; Michelle DeYoung is a reliable if rather neutral Waltraute, not helped by van Zweden’s uncertain pacing of the scene. Norns and Rhinedaughters contribute well.

Van Zweden keeps everything moving at a good clip but seems to respond more emotionally to certain scenes than to others. After a rather uncertain Norns’ scene the Dawn Duet and Rhine Journey go with terrific panache, an impact later rediscovered in the big ensemble scene of Act 2 after Brünnhilde is brought back from the rock. He is (unsurprisingly) not yet so sure of what all the music means, or relates to, and those little instrumental decorations which Barenboim, for example, colours and places so precisely (hear the 2013 Proms performances, if you can) tend rather to go for nothing. Also, more surprisingly for a noted Brucknerian, energy tends to drain away from slow-moving passages, which makes some of the final Immolation hang fire.

There are now so many Rings available at discounted prices that, in both marketing and artistic terms, it’s no longer possible simply to give this newcomer of very real merits a special bargain option box in some collectors’ batting order of desirability. The best of this latest instalment and its predecessors has that unique excitement that comes from a major task attempted for the first time. There’s little dull here, it always sounds good and it could make for an ideal economic first-time listen to the work. A selection of important rivals: Clemens Krauss (Pristine), Wilhelm Furtwängler (Pristine twice), Joseph Keilberth (Testament) and Daniel Barenboim (various).