Women directors are still enough of a rarity in opera to be notable as such, and not least when they turn the tables on the Man-as-Hero/Woman- as-Victim formula that drives so much of the repertory.

Katie Mitchell's fascinating WNO Don Giovanni, which has just opened in Cardiff, is a case in point: her first opera staging in a career which has so far been based at the RSC. And it comes with a clean, fresh, wholly justifiable re-reading of the text that knocks Giovanni off his pedestal as the star of the show and substitutes the trio of Zerlina, Anna and Elvira: victims if you must (Zerlina has a black eye to prove it) but metamorphosed by the end into an agency of vengeance worth a TV mini-series. These are tough, resourceful women - even Elvira, who is reined in from the purlieus of comic pathos - and they transform the awkward charm of the epilogue into something purposefully vital, laying claim to Leporello's catalogue and burning it.

In fact, the whole tone of the production is deducible from the way it has been advertised, restoring the full original title with telling graphic emphasis: Il dissoluto punito (big print) ossia Il Don Giovanni (small). On stage as on the posters, this Don ends up reduced - quite elegantly done by Italian baritone Davide Damiani but with a stiffness in the singing that qualifies its musicality. And generally the men here are no match for the women, with an interesting but vocally limited Leporello and an Ottavio (Gwyn Hughes Jones) whose strong, still-developing tenor has enormous promise but here rides roughshod through the tender beauty of his arias. Against that there's a luscious Elvira from Alwyn Mellor, a striking (if slightly monochrome) Anna from Cara O'Sullivan, and a fine Zerlina from Catrin Wyn Davies - all utterly credible in 1940s costumes which fit the spirit of the piece far better than the vacuous contemporary chic of Deborah Warner's Don Giovanni at Glyndebourne.

Comparisons with that Glyndebourne staging are hard to resist and, on every count, favour WNO. Warner never knew where she was going with the text: Mitchell does, and comes up with very viable answers to its shortcomings. For once, Don Ottavio has some reason for his Act II declaration that there can now be no doubt of Giovanni's culpability (a blood-soaked handkerchief in the Don's pocket); and interestingly, it's not Giovanni who exits at the end of Act I but The Avengers - out of their depth in the moral anarchy of the party scene and clearly at a loss to know the etiquette of dealing with a Don dressed in a frock and feather boa. Well, Viva la liberty bodice, as Da Ponte nearly wrote and Freud might have added. All told, it makes a keen impression and a happy debut on the lyric stage for its director. Carlo Rizzi conducts with a comparable sense of enquiry and occasionally explosive attack; and if you get more from the starrier Giovanni coming soon to Covent Garden, I'll be surprised.

The LSO opened its 1996-97 season on Tuesday with a new Cello Concerto by Colin Matthews, played by Mstislav Rostropovich, conducted by Colin Davis; and it proved a richly colouristic score that stalked the ominously exotic world of Tippett's Triple Concerto, with contemplative outer movements content to gaze on their own, spacious beauty. The weakness was a busy middle movement that should have been pivotal but felt emptier than anything around it; and Rostropovich's playing was more charisma than precision. But no matter - it was attractive writing, and practical in its handling of the balance between soloist and orchestra: the snag which has pursued cello concertos through history.

ENO has just revived its smart, unsentimentally post-modern Robert Carsen production of Britten's A Midsummer Night's Dream, with a new, beautifully sung but unethereal Oberon (David Daniels), a stunning new Puck (Miltos Yerolemou) whose athletic brilliance compensates for the fact that he isn't the husky adolescent Britten wanted (so badly), and Lillian Watson defying her years yet again as a superlative Tytania. But it reminded me that this piece contradicts everything I said in a talk last week to a group of prospective opera composers and librettists. Good libretti, I said, are not play-texts set to music, still less self-sufficient poetry; and the libretto for the Dream is - er - exactly that, taken direct from Shakespeare, albeit with cuts. But then, working with a centuries-dead writer is no role model for creative collaboration, which is what the talk was meant to be about.

It was a contribution to a project called Opera Lab which runs every summer in a farmhouse in Kent and is effectively a cross between an Oxbridge reading-party and a marriage bureau. Ten or so writers and composers with an interest in opera are invited to stay for a week, find out about each other and make relationships from which some piece of work, however fragmentary, is expected to result. Immediately to hand they have a stage director (Stephen Langridge), conductor, choreographer (Kenneth Tharp), several pianists, and a group of singers led by Jane Manning who assist as needed and finally showcase the work before an invited audience of opera company representatives.

It follows that Opera Lab is partly a shop for emergent talent and ideas. More important, it's a "safe house" for experiment and a small but serious assault on the high casualty rate which has afflicted new opera since opera was new. Compare the 200-odd works which have genuinely made it into repertory with the thousands written in the past 400 years and you get some idea of the problem - for which, of course, there are varied reasons. But one is that opera is a complex apparatus with limited access to the development stages any modern musical would pass through before it dared present itself as finished work. Another is that opera is a shotgun marriage between disparate disciplines whose practitioners are unreasonably expected to collaborate by instinct. They are certainly not trained to work together; one of Opera Lab's telling discoveries is the degree to which writers and musicians are innocent of each other's craft. That the history of operatic collaboration comes written largely in blood is hardly surprising.

Opera Lab isn't the only development space of its kind, but to my knowledge it's the only one not tied to a specific opera company with a brief to feed commissioned works into the system. It's a general nursery with a broad learning agenda - although the intake is carefully selected. The class of '96 included composer David Knotts working on a transvestite love-quest narrative (Fidelio: the remake) with poet Ian Duhig; a fantasy on Anne Boleyn by TV playwright Stephen Plaice with Ukrainian composer Julia Gomelskaya; and a retold Indian myth by Rukhsana Ahmad working with the prodigiously bright young British composer/ pianist (currently based at Harvard) David Horne.

To the extent that I could judge - I wasn't there throughout - some of these miniatures had the potential for an enlarged ongoing life, some not. But the important thing was that the composers and writers had tested the water and tested their own aptitude for a genre that doesn't suit allcomers, however accomplished. Think of Haydn.

For the ideas that do show potential there would ideally be an Opera Lab II to nurture them on; but as Opera Lab I only survives on modest budgets courtesy of occasional backers like the Jerwood Foundation, that isn't feasible - unless the Lottery were to step in under its new terms of reference to fund developing talent. Given the public money that ultimately goes to waste on operatic failures, the Lottery Board could consider it an insurance premium.

`Don Giovanni': WNO (01222 878889), continues Tues & Fri. `Dream': ENO, WC2 (0171 632 8300), continues Wed & Fri.