Like his earlier musicals Follies and Company, Stephen Sondheim’s 1981 show Merrily We Roll Along is set among the sophisticates of New York – and in this case also Los Angeles, for Frankie, the central character, successful composer Franklin Shepherd, does indeed go to Hollywood.

The musical actually rolls along backwards. We see fortysomething Frank lionised in the (1981) present and then watch his life, inextricably intertwined with his two erstwhile best friends Mary and his lyricist Charlie, unwind to where they began as fresh-faced students in the 1950s. How did the young idealist become the celebrity? In the words of a key song “How did you get here from there, Mr Shepherd?”

His story in reverse is painfully clear. Success comes at the price of crumbling relationships, all signposted with irony, sometimes cruel, sometimes touching. The music brilliantly unravels too, for example “It’s Our Time” reverts from sophisticated anthem lauding ‘movers and shapers’ to simple optimistic song of youthful beginnings, hopes and aspirations.

John Doyle’s signature production for actor/musicians is blessed by Catherine Jayes’ ravishing musical and vocal arrangements, enhanced by Gary Dixon’s sound design – and with a formidably talented, versatile cast. But although they’re all used to rising to the challenge of acting, singing and playing – often simultaneously – here, it sometimes makes the production feel like a semi-staged concert performance. It’s curiously static – perhaps because of Liz Ashcroft’s tunnel-like set, dominated downstage by Frank’s iconic grand piano and upstage by a reel-to-reel tape machine, symbolic of the unspooling story, leaves little room for manoeuvre.

Frank (Sam Kenyon) spends most of his time at the piano – no bad thing for he’s a consummate pianist. And the instrument is literally a star vehicle for Rebecca Jackson’s ruthless femme fatale Gussie, Frank’s predatory leading lady and second wife, who’s usually draped over it.

Although Merrily is a tale of soured relationships, here the first half is perhaps too dark and humourless. Charley’s virtuoso rant “Franklin Shepherd Inc”, publicly humiliating Frank on a primetime TV chat show for selling out to commercialism, loses its dark humour in Thomas Padden’s ferociously angry delivery; although Elizabeth Marsh’s Mary makes a better fist of the drunken sarcasm born of disillusionment and unrequited love for Frank.

But in the second half as the story focuses on sunnier youthful aspirations, the pace quickens, the mood lightens and there’s much to enjoy. The revue sketch sending up the Kennedys taking over the White House - a brilliantly funny, credible pastiche of satire from young writers - is especially effective, as the performers execute a gleeful Irish jig complete with instruments. And Joanna Hickman’s Beth makes the most of her transition from wronged wife back to gutsy aspiring young star.

- Judi Herman