Keith Warner’s production of Wagner's Der Ring des Nibelungen was first seen at Covent Garden between 2004 and 2006, and is now back for a third and final series of full runs, chiefly to catch the Brünnhilde of Nina Stemme in three of the operas, continuing into November.

Two rules should help the non-Donizettian: avoid all stagings of the prolific Bergamasco's nearly 70 operas other than the comedies; and seek the guarantee of top bel canto stylists. Conductor Mark Elder and soprano Joyce El-Khoury certainly fit that bill, and a straight concert performance of L'Ange de Nisida, given at the Royal Opera in association with Opera Rara, got it exactly right.

Striking it lucky with a successful new opera is a rare occurrence, though every company has a duty to keep on trying. The Royal Opera hit the jackpot with 4.48 Psychosis, a highly original approach to Sarah Kane's profound and authentic play by Philip Venables, the first Doctoral Composer-in-Residence on the scheme initiated by Covent Garden in alliance with the Guildhall School of Music and Drama. How could one not wish his successor, Israel-born Na'ama Zisser, all the best?

It's awfully long for a fairytale in which a mystery prince helps a damsel in distress, and she asks him the question she shouldn't. Myth tends to go deeper, as Wagner did in The Ring of the Nibelung after Lohengrin. Here he captures the magic of transformation and transcendence, but in between there's too much hard-to-stage pomp.

A rope is mercy; a razor-blade to the throat, a kiss; a red-hot poker… But, of course, we never get anything so literal as the poker in George Benjamin and Martin Crimp’s elegant, insinuating retelling of Christopher Marlowe’s Edward II.

Depression, with or without psychotic episodes, is a rare subject for drama or music theatre - and with good reason: the sheer unrelenting monotony of anguish and self-absorption is hard to reproduce within a concentrated time-span.

Anyone who's seen Richard Jones's rigorous production before will remember the makeover – Katerina Izmailova, bored and brutalised housewife released by sex and murder from her shackles, having her drab bedroom expanded and redecorated in deliberate incongruity with Shostakovich's most shattering orchestral music – and its polar opposite, the near-black horror of convicts in trucks by the river on their way to Siberia.

With the eyes of musical fashion turned relentlessly on the calculating stage works of chilly alchemist George Benjamin, hopes ran high for a brighter spark in a new opera by his contemporary Mark-Anthony Turnage.

A political prisoner is brutally initiated into the life of a state penitentiary, and leaves it little over 90 minutes later. Four inmates reveal their brutal past histories with elliptical strangeness - each would need an episode of something like Orange is the New Black - and two plays staged during a holiday for the convicts take up about a quarter of the action.

Roll up, dépêchez-vous, for Carmen the - what? Circus? Vaudeville/music-hall/cabaret? Opéra-ballet, post-Rameau? Not, certainly, a show subject to the kind of updated realism which has been applied by just about every production other than the previous two at Covent Garden.