Sir John in Love Coliseum, London WC2, Sat to 1 April

In 1913, as musical adviser to Frank Benson's Shakespeare company in Stratford-upon-Avon, Ralph Vaughan Williams composed incidental music for a production of The Merry Wives of Windsor. It included an arrangement of the English folk tune 'Greensleeves', which a decade later he recycled into the score of an opera called Sir John in Love. These were supposedly Elizabeth I's words after seeing the first part of King Henry IV. Told that Her Majesty liked Falstaff so much as to wish to see 'Sir John in love', Shakespeare knocked off The Merry Wives in 10 days, apparently none too pleased to be diverted by royal command from his second historical tetralogy.

It is far from being the Bard's best play, and makes for a lightweight if fitfully entertaining opera. Only 30 years after Verdi's Falstaff which incorporates the Henry IV plays into a major masterpiece, the English composer mustered the nerve to use the same play as the basis for his own third opera, weaving lines from Middleton, Jonson and other contemporaries of Shakespeare into his own libretto. This quintessentially, at times insufferably English work is now being mounted for the first time by our English National Opera company. Director Ian Judge plays it safe with a highly traditional staging, throwing in some much-needed sight gags (such as Falstaff downing a pint in one go), and saving the best for last with a Windsor Forest at midnight lavishly rendered by designer John Gunter.

Before that, Falstaff's amorous antics are set in the world less of Shakespeare than Jerome K Jerome. The leading characters affect a rural accent more West Country than Warwickshire, let alone Windsor.

ENO favourite Andrew Shore finds his defining role in the title character, which makes as much use of his comic timing - right down to his trademark double-takes - as his famously lusty lungs. Mistresses Ford and Page are in the safe hands (and throats) of Jean Rigby and Marie McLaughlin, with saucy support from Sally Burgess as Mistress Quickly, and good solid husbands in Alastair Miles and Russell Smythe.

There are stylish contributions from Andrew Kennedy, Robert Tear, Iain Paterson, Stuart Kale and others in a 20-strong cast who are, most unusually, all British - with a half-Russian, half-Italian conductor in Oleg Caetani, still billed on the posters as ENO's new music director, though he has fallen prey to recent management upheavals. Now lush, now skittish, occasionally ravishing, Vaughan Williams's score is accorded the Rolls-Royce treatment befitting this Model T Ford of an opera, which will probably prove a much-needed hit for embattled ENO.

Wozzeck Covent Garden, London WC2, Tues to 13 March

Keith Warner's powerful 2002 staging of Berg's Wozzeck at Covent Garden raised such high hopes for his subsequent Ring cycle that disappointment was perhaps inevitable. Before its final instalment, Gotterdammerung, opens at Easter, his Berg has returned (restaged by Matthias von Stegmann) to remind us of what might have been. Warner and designer Stefanos Lazaridis take a minimalist approach, leaving the stage bare enough - apart from three Expressionist glass tanks, in one of which the protagonist finally drowns - to focus attention on some high-calibre performances, in a work exposing its soloists' acting skills as much as their vocal abilities.

All deliver as memorably this time around as did the fine original cast. In the title role the Danish bass-baritone Johan Reuter proves a worthy successor to Matthias Goerne, offering a masterly portrayal of the downtrodden social victim Berg sought to emphasise when adapting Buchner's play. He has an equally forceful partner in Susan Bullock, making her belated Royal Opera debut as a slatternly, powerfully sung Marie, ill-fated mother of his child.

There is a constant air of grotesquerie befitting this pathetic, affecting tale of an innocent doomed merely by his unworldliness. The Austrian bass Kurt Rydl and British tenor Graham Clark make a terrific double act as the Doctor and the Captain capering about in neo-Brechtian style as they sing their lungs out in the spooky laboratory where the hapless foot-soldier is just another kind of victim. The Finnish tenor Jorma Silvasti also swashbuckles to great effect as the dastardly Drum Major who precipitates poor Wozzeck's demise. Daniel Harding takes imperious command in the pit, wrenching every ounce of unease, sadism and suffering from this relentlessly searing score. But the image that lingers in the mind, as Berg intended, is that of the child onstage throughout (played on the first night by a confident young Remi Manzi) who will so clearly inherit his parents' involuntary flaws and perpetuate their undeserved agonies.

Osvaldo Golijov Barbican, London EC2

The Argentine-born composer Osvaldo Golijov, now domiciled in Boston, first attracted international attention with his La Pasion segun San Marcos, now given its British premiere at the Barbican. Commissioned in 2000 to mark the 250th anniversary of Bach's death, the work bears minimal resemblance to the masses of the great master. A mish-mash of Latin-American samba and tango influences, Colombian drums, Afro-Brazilian dancing and feisty gospel-style singing, filtered through occasional echoes of Bernstein, even Kurtag, from a small European-style string orchestra, it held an enthusiastic audience rapt for 90 minutes but made a mark more visual than aural.

Based on St Mark's gospel, the Spanish text lends the story of the Crucifixion contemporary resonance by turning it into a universal parable of injustice. The solo dancers and cabaret-style singers added a vivid edge of protest to the passionate commitment with which it was performed by the Orquesta la Pasion and the Schola Cantorum de Caracas under Maria Guinand. But the piece lacks the cohesive architecture of similar contemporary works such as John Adams's El Nino, also recently performed at the Barbican. A terrific rhythm section, in particular, left the impression that Golijov's most substantial piece to date was really more suited to performance in the streets - perhaps, appropriately last week, at Mardi Gras - than in a concert hall.