Niobe, Regina di Tebe, Royal Opera House, LondonFidelio, Wales Millennium Centre, CardiffTristan und Isolde, Royal Festival Hall, London

Lust, ambition, and a good dose of grief...they knew how to tickle an audience in 1688

The alpha mother is not a modern phenomenon.

Today you might see her at the school gates, boasting of Jack's hockey captaincy, Emily's flute recital, and the new baby's congenial sleep pattern, her 4x4 stuffed with bamboo nappies and Bond Papers. Lesser parents may roll their eyes but excessive pride in one's offspring rarely merits punishment of the sort meted out to Niobe, whose children (14 according to Ovid, 12 according to Homer) were slaughtered on Leto's command. After grieving for nine days, poor, vain, fecund Niobe was turned to stone, still weeping.

Infanticide and petrification are but two elements in Agostino Steffani's 1688 opera, Niobe, Regina di Tebe, brought to the Royal Opera House by Thomas Hengelbrock and the Balthasar -Neumann Ensemble in Lukas Hemleb's haute-couture production. Composer, diplomat and theologian, Steffani knew how to tickle the interest of his audience, spiking Niobe's maternal hubris with adultery, magic spells, political intrigue, romantic sub-plots and the stock sardonic nurse who is there to comment on human folly. The opera was premiered in Munich's carnival season, and it shows. So do the diverse musical influences in Steffani's life: the stile antico training of his boyhood, an early baptism in Venetian opera, and a pivotal journey to Lully's Paris. Lust, ambition and grief are expressed extravagantly yet succinctly. The arias are brilliant and abundant, propelled by athletic ground basses, interrupted by prowling kettle-drums, or sinuously laced with viola da gamba.

Raimund Bauer's black-walled set is an elegant frame for the dazzling effects required: celestial spheres, the entrance of Mars (actually Creonte), the earthquake that destroys the brattish fruits of Niobe's womb. Looking a million dollars in Andrea Schmidt-Futterer's crushed-silk gowns, Véronique Gens presents a complex, tart and sexually confident Niobe, her voice as cool as chilled white burgundy in the pitiful transformation scene. Her poise is not matched by Jacek Laszczkowski (Anfione), whose chromatic sobs sound like an elderly aunt coughing into a handkerchief. As his two rivals, Clearte and Creonte, Tim Mead and Iestyn Davies outperform him, the latter projecting with uncanny sweetness and ease.

In the pit, it's sublime: a thick, glossy seam of violone and tar-black regal organ, limpid recorders, agile strings, delicate and daring improvisations from double-harp, theorbo and guitar. The last performance is this afternoon, but for those with air miles to spare, Boston Early Music Festival has a new production next year, with Amanda Forsythe as Niobe and Philippe Jaroussky as Anfione.

So from hubristic mothers to perfect wives. First seen in Bordeaux and now taken up by Welsh National Opera, Giuseppe Frigeni's perverse staging of Fidelio is all sing and no spiel. The choreography is distracted and dreamlike, the dialogue largely excised, leaving silences of no discernible metre or purpose. At the second performance, the audience eventually filled some of these with applause, rather grudgingly. It takes a lot to muddy the radiance of Beethoven's score, but Frigeni manages it, despite the best efforts of conductor Lothar Koenigs, the orchestra, and a respectable supporting cast.

The wrong shape and size to pass as a boy, even by candlelight, Lisa Milne (Leonore/Fidelio) sings with customary musicality, while veteran tenor Dennis O'Neill stretches credibility as the Enlightenment fire-brand, Florestan.

Bill Viola, Peter Sellars and Esa-Pekka Salonen's Tristan Project finally reached London last week in the Philharmonia Orchestra's Royal Festival Hall performance of Tristan und Isolde. Clothed in golds and Marian blues, Viola's meditative video triptych has been a constant since the project's inception in Los Angeles, suggesting, if not dictating, Salonen's pace. Impressive in the Opéra Bastille staging of 2005, Salonen's reading was astonishing in London: audacious in its measured embrace of silence in the Prelude, tumbling with urgency in Act II, wretched with misery in Act III.

Though billed as a semi-staging, this surround-sound Tristan had tremendous dramatic vitality, using the building to great effect, with Anne Sofie von Otter's Brangäne poised like an anguished angel in the highest box. Violeta Urmana's Isolde was smooth and elegant, Gary Lehman's Tristan a credible soldier, goofy with love, sick with shame. Joshua Ellicott's bright, edgy Sailor/Shepherd and Stephen Gadd's bitter Melot were outstanding in a strong supporting cast. The highest praise, however, must go to the orchestra, whose stamina, discipline and sustained glow were stunning.

'Niobe, Regina di Tebe': (020-7304 4000 - 3pm, today. 'Fidelio' (029 2063 6464) to 8 Oct, then touring

Next Week:

Anna Picard prepares to shiver at Opera North's Turn of the Screw