Mahler's Conversion, Aldwych <br></br>A Day in the Death of Joe Egg, New Ambassadors<br></br>Nightingale and Chase, Royal Court<br></br>Don Juan, Crucible, Sheffield

Heavens above! Herr Mahler is in a bit of a tizz

Antony Sher is whirling his arms around, possibly in a last ditch attempt to upstage the weather. In Mahler's Conversion – Ronald Harwood's new West End bio-drama – Sher embodies the Romantic composer and conductor, darting about like a manic gnome under a skyscape of gathering storm clouds (Stephen Brimson Lewis's grand design). Once or twice, our Gustav is nearly engulfed in billowing dry ice. At other times, when he works himself up into a passion and we hear pre-recorded bursts of his symphonies, the heavens above burn crimson. Not exactly in harmony, I reddened with embarrassment at the OTT points in this show.

Meanwhile, Harwood charts Mahler's life from 1897 with little artistic flare. Pals of the Bohemian-born maestro discuss how close he is to achieving his dream of running the Vienna Opera. Comic relief and some love interest are supplied by his mistress – soprano Anna Von Mildenburg – dashing into the parlour topless. Next we discover Mahler values pragmatism over his spirituality as – exasperated by anti-Semitism – he abandons his Jewish roots and converts to Catholicism to land the job. Soon he's seduced by Viennese belle Alma Schindler and dismisses old friends who find her intolerable, all the while insisting she sacrifice her musical ambitions and play the devoted wife. By the closing Act, he's a transatlantic big shot but cursed with impotence. Meeting Sigmund Freud for a session, he discusses his limp, mother complexes, faith, guilt, divided identities and essential Jewishness.

In highlighting religio-racial tensions, Mahler's Conversion touches a contemporary nerve. Beyond that, any playwright embracing grand themes should inspire gratitude. But Harwood makes his characters spell out the big issues. Gregory Doran's production tries hard to counteract such shortcomings. Anna Francolini (playing the mistress) contrives to be both histrionic and funny, hurling herself on chaises longues. Gary Waldhorn delights as a wry, humane Freud. But Fiona Glascott's Alma is crudely played as brazenly nasty. As for Sher, he uncannily resembles Mahler with round specs and high forehead, and he captures the legendary energetic egomania. Yet this is an excessively showy performance. Pseudo-poetic declamations are milked for considerably more than they're worth. And when Sher starts leaping and spinning in a black cape amid thunder claps, one longs for a still voice from on high to mutter, "Ritenuto e pianissimo. P-u-r-lease!''

Moving on, the septuagenarian Bristol-born playwright Peter Nichols is refusing to go quietly. He's been enjoying a comeback since the Donmar's hit revival of Passion Play. Now his polemical early tragi-comedy, A Day in the Death of Joe Egg, has rolled into the New Ambassadors with Clive Owen and Victoria Hamilton playing Bri and Sheila.

Back in 1967, Nichols's semi-autobiographical depiction of this couple broke taboos of decency. Struggling to cope with a brain-damaged child, they share jokes over her mute, writhing body. In Laurence Boswell's admirable revival – with a fragile, paper-thin living room designed by Es Devlin – Owen and Hamilton's mix of stressed-out cruelty and devoted care is still sharply unsettling. Hamilton (the Judi Dench of her generation who never puts a foot wrong) laughs along with her spouse then segues into monologues welling with sorrow, while Owen is a laid-back jester with a despairing, destructive side unleashed in a life-threatening climax. Prunella Scales is also a farcical and chilling mother-in-law, knitting a cardie while pouring conversational acid over Sheila's marriage.

The snag is that Nichols's theatrical games feel dated and rather naïve. When Bri and Sheila step out of the naturalistic action to replay past traumas – impersonating incompetent doctors as if improvising a sketch show – then the comedy seems evasively shallow. Nonetheless, cracking in parts.

Another marriage is on the skids in Nightingale and Chase. Zinnie Harris's new two-hander – staged at the Royal Court Upstairs by Richard Wilson – is initially riveting. Christopher Fulford's Nightingale sits spotlit in a white cell (minimalism courtesy of Angela Davies). He's a cockney businessman recalling the evening he collected his wife Chase – a repeat offender – from prison. He intended to charm her with dinner for two ("Candles, fizzy wine – kid out of the way''). This plan laughably bites the dust, although Harris weaves in more ominous hints of a crime thriller. Fulford is strangely threatening with his arms hanging lifeless, his eyes glittering. Unfortunately, the suspense slackens during the second monologue by Jody Watson's Chase, mainly because Harris's condensed poetic style becomes a tad monotonous.

Last but far from least, Tom Hollander is wickedly funny as the serial womaniser in Molière's Don Juan at the Sheffield Crucible. Michael Grandage's production is played out in an attractively dilapidated, Mediterranean town square and Hollander is having the time of his life, relishing Simon Nye's zesty new translation and skipping after ladies like a naughty boy. With designer crocodile shoes and golden curls, he's also a nasty toff and fallen angel with no faith at all. What's startling is this brief comedy's hidden depths. Lucy Briers, as the foolishly smitten rustic, Charlotte, is a painfully real person not merely a pastoral caricature. And morally, the myopia of Anthony O'Donnell's slacker Sganarelle is terrifying as – assuming he won't share his master's day of reckoning – he stands over the pit of hell screaming, "My wages! My wages!''.

k.bassett@independent.co.uk

'Mahler's Conversion': Aldwych, London WC2 (0870 400 0805), booking to 2 Feb; 'A Day in the Death of Joe Egg': New Ambassadors, London WC2 (020 7369 1761), to 24 Nov; 'Don Juan': Crucible, Sheffield (0114 249 6000), to 20 Oct; 'Nightingale and Chase': Royal Court Upstairs, London SW1 (020 7565 5000), to 27 Oct