Movin' Out feels and tastes like a loaf of processed sliced white bread with margarine, not butter. Rock concert and dance staging meet in a middle-ground medley of mediocrity. The subject is: America goes to the Vietnam War. Kids have a dance, some kids die, others hang out in a bar, the bereaved get through. Old friends survive.

Billy Joel songs, and a raucous, banal rock band, are the backdrop. The songs – not one of which I recognised apart from the mildly irresistible “Uptown Girl” – are a fusion of Elton John and Ray Charles lacking the melodic bounce of the first and the black mystery of second.

Twyla Tharp, who conceived the show and directed it, is a legend of modern choreography. Here, she is obviously, and admirably, building up her pension fund (next up for show-time, I gather, is the Bob Dylan song book). But surely she knows that the music has no originality, composed as it is entirely of rock and jazz clichés and a shameless lift from the slow movement of a Beethoven piano sonata. Her choreography is interesting, startling, vigorous, but dated in its fusion of ballet, jazz and jive.

Still, the execution is unarguably magnificent. We must instantly salute Holly Cruikshank and Ron Todorowski, who dance their socks off for two hours and display incredible technique and stamina. Holly is a human dynamo, possibly seven feet tall, who seems unencumbered by gravity, or indeed rules, of any kind. Ron is a gas, brilliantly expressive and limber, permanently suspended, it seems, six feet above the ground with his legs splayed in opposite directions. Chipping in powerfully towards the end is Laura Costa Chaud as a pint-sized grieving girlfriend who finds a new direction and a new groove. The finale is predictably up-beat, all sorrow gone, all future happy.

Standing in as Joel, the piano man James Fox tries to make a convincing concert of all this but falls several leagues short. His band pump away with plenty of grease – guitars, saxophones, trumpets – but there’s no vintage Buick to get on the road.

Not one item is half as good as any song in Andrew Lloyd Webber's Whistle Down the Wind. And, as musical theatre, it has no sense of dynamic progression or anything much else except perhaps for grown-up Fame addicts or happily short-changed Bruce Springsteen fans.

- Michael Coveney