What makes a good piece of theatre? Is it the atmosphere generated? Is it the acting? Or is it the ability to communicate ideas clearly? I don’t mind if sometimes I can’t hear or understand words. In the past, I have been overwhelmed by Polish versions of Dostoyevsky’s The Idiot. I have watched open-mouthed at Kabuki without surtitles and when Federico Garcia Lorca’s Yerma was first seen in this country, in Peter Daubeny’s World Theatre seasons, back in the Sixties, you hardly needed to understand Spanish to be so desperately moved by the sense of yearning emanating from a production played out on a giant trampoline that looked like an enormous cat’s cradle. Lorca, it turns out, is the chosen author for a new production that has its own issues.

It's tough being a critic.

Of course she isn't now the watchful, learning 29-year-old who premiered Covent Garden’s opulent, sensually loaded production in 1995, but Gheorghiu’s varicoloured voice - a rainbow of tears, sobs, scoops, warbling runs and top notes that seem to rack her body with pain - has if anything added more colours since then (including a less fetching jeune-fille timbre in the middle that sounds as if it’s hiding a problem).

What kind of play is Frank Wedekind's Lulu? The answer is a very odd one, with a fractured writing history. Wedekind subtitled his original five-act exploration of raw femininity, in 1894, "A Monster Tragedy", then divided it into two: Earth Spirit and Pandora's Box.

Usually a seasonal home for the pastel-coloured delights of drawing-room farce, musical comedy and the odd Shakespeare pastoral, Regent’s Park Open Air Theatre is this year offering a programme of rather darker hue. With Macbeth to follow later in the season (not to mention Stephen Sondheim’s deliciously off-white fairytale musical Into the Woods) it was with a new production of Arthur Miller’s The Crucible that things kicked off last night.

A young Arthur Miller wrote this highly moralistic, redemption-seeking play soon after the Second World War, a parable about an older generation’s dubious pragmatic principles versus the bewildered idealism of their children who were Miller’s generation, the soldiers’ generation. The deathlessness of its message about faulty army equipment, young military casualties and the no-blame culture may be quite as much a reason for this new revival of Howard Davies's 2000 National Theatre production, now with David Suchet and Zoë Wanamaker.

The recent fuss about British culture being anti-Catholic just because some civil servant wrote a spoof memo satirising the Pope’s upcoming visit may have been overblown, but it is certainly true that, in the past, Italy was a byword for rank corruption. To doughty English Protestants, Rome was a stew of sin and Italians were Machiavellian plotters and idolators. Little wonder that Thomas Middleton’s 1621 tragedy, a large-stage revival of which opened yesterday, is brimful of illicit sex, cunning intrigues and vicious revenge - and set in Renaissance Italy.

It's amazing how much you can tell of what lies ahead from the way a conductor handles a master composer's first chord. Katya Kabanova's opening sigh of muted violas and cellos underpinned by double basses should tell us that the Volga into which the self-persecuted heroine will eventually throw herself is a river, real or metaphorical, of infinite breadth and depth. And that was exactly what Mark Wigglesworth conjured from ENO strings in a performance more alert to the value of every note and colour in Janáček's lightning-flash score than any I've heard. 

Arthur Schnitzler belonged to a culture of inquiry and experiment, in which dreams and desire were crying out to be articulated and delineated; sexual needs were the unexplored stuff of life - how well Vienna painters like Klimt and Schiele knew this - and, as Freud worked it all out for us, not necessarily dangerous. Where better to bring this to flesh-and-blood life than on stage?