Porgy and Bess, Savoy, London <br/> Orestes, Tricycle, London <br/> Scenes From the Back of Beyond, Royal Court Upstairs, London

It ain't necessarily so. As a rule, in the arts hierarchy, an opera is rated above a musical. But Trevor Nunn is challenging this rule with his deft and sometimes storming musical reworking of Porgy and Bess. George Gershwin's 1930s self-styled "folk-opera for black voices" has been substantially reorchestrated here - with the recitative removed - but it remains poignantly set in a poor, racially downtrodden but resilient community in South Carolina. Here Bess, the local scarlet woman, is torn between a reformed life with a good-hearted man, Porgy, and the lure of addictive vices - namely prostitution, drugs and her bad-boy ex-, Crown.

As soon as Lorraine Velez's Clara wanders across the scruffy tenement courtyard of Catfish Row - singing the opening lullaby, "Summertime", to her baby - this version feels closer to life, more natural. Operatic sopranos always make that song sound over-polished. Here the melody's underlying lovely, relaxed lilt is allowed to come to the fore. Later, too, when Clarke Peters's crippled Porgy feels blissfully happy - having landed Nicola Hughes's Bess as his sweetheart - he breaks into "I Got Plenty O' Nuttin'" as if he's just softly singing to himself while he works.

Some may discern an irony in the fact that Nunn's past Glyndebourne production of Gershwin's full score persuaded some sniffy music critics to belatedly recognize Porgy and Bess as a great opera, only for the same director and his musical arranger, Gareth Valentine, to technically take it down a notch now. It's essentially the same staging, but here the orchestra is much smaller and the vocal range of the songs has been reduced too. Even with that adjustment and amplifying microphones, one or two of Peters's and Hughes's notes sound strained. However, a husky timbre and faster tempos actually bring the songs closer to the street talk that replaces the recitative with winning vivacity. Melanie E Marshall's feisty Maria also gets a solo, "I Hates Yo' Struttin' Style", wittily spoken in rhyming couplets like an early rap number - rapping druggies over the knuckles.

Nunn and his designer, Paul Gunter, are not so great when it comes to conjuring up a hurricane. Cornell S John's muscle-bound Crown leans into a supposedly almighty wind at the door whilst the curtains at the broken windows barely flutter. That said, there are no weak links in the acting; several ensemble dance routines get swinging with cheeky jubilation; and the rich harmonies of the ensemble chapel choiring, with surging spirituals, are positively oceanic. In the face of tragedy, this community's rallying Christian faith and hope seem ultimately uplifting - if optimistic.

In another new adaptation, Shared Experience's favourite writer Helen Edmundson freely confesses that she has played around with Euripides's Orestes. This rarely staged drama unfolds just after Clytemnestra's murder as her son, the matricidal titular prince, faces a public trial. His claim that a divinity is on his side sounds like dangerous madness, with perhaps a trace of our contemporary world leaders. Guilt-crazed, he insists Apollo told him to revenge Agamemnon's death, and he begs his uncle Menelaos to defend him. Once let down, he goes on the rampage.

Though Ancient Greek drama may have been half-way to opera or musical theatre, Nancy Meckler's production features only one song and no dance. Edmundson has axed the Chorus as well as Pylades (Orestes's best friend and accomplice) and the closing deus ex machina. Also, it must be said Niki Turner's set design, though gold-sprayed, looks scrappily low-budget - more IKEA than ancient Argos. The final coup de théâtre is laboured as well, involving pulleys when Orestes has to leap off a parapet. One can only presume that he and Hermione, the kidnapped baby in his arms, will survive the fall to continue the family saga and later get engaged.

Still, Euripides delighted in adding startling twists to established myths, so why shouldn't Edmundson? Moreover, what emerges is a chamber play shot through with poetic images and fraught with emotional intensity. And Alex Robertson as Orestes, after a wobbly start, gains delirious momentum, kissing his sister, Electtra, with a desperately abandoned passion on the brink of death.

In Meredith Oakes's new play, set in suburban Australia in 1959 and entitled Scenes From the Back of Beyond, a small boy called Guy drifts in and out, looking morose. He has, we gather, recently set a broom alight in someone's backyard and run around yelling "I'm God and I'm going to destroy the world." This glimpse of a psycho-in-the-making unsettlingly chimes with Orestes, last seen screaming "Look I am a God" while launching off the burning palace. And, indeed, Oakes appears to share Edmundson's concern about youngsters behaving ruinously as a result of inattentive or divided parents. Guy's dad, David (Daniel Lapaine), is admiringly befriended by his neighbour, Martin Turner's Bill, who naively regards David's work in atomic physics as heralding a utopian future. But David is a screwed-up cad. While Bill and his unhappy wife, Penny Downie's Helen, are quarreling about their miserable sex life and lapsed socialist principles, David embarks on an affair with their underage daughter, Jasmine (Samantha Losey).

Alas, director Ramin Gray (stepping in to replace Annie Castledine) has not managed to spark life into any of this. There's passing talk of conductivity, particles hitting off other particles, time and motion, yet, in theatrical terms, the evening seems bemusingly turgid. Though perhaps intended to be poetically stylized, the character's long monologues come over as stiff and disconnected - though a few flashes of dry wit and sharp griefs are scattered through this desert. Bill's sad marital confession to Guy - "I've always lived with her with one eye on the exit" - sticks in the mind.

k.bassett@independent.co.uk

* 'Porgy and Bess' (0870 164 8787) booking to 31 March; 'Orestes' (020 7328 1000) to 2 December; 'Scenes From the Back of Beyond' (020 7565 5000) to 25 November