The City Sings, Barbican, London

When it's lit up at night, the office block facing the entrance to the Barbican looks like the embodiment of capitalism. The rows of cubbyholes stretching heavenwards are all identical, each with the same standard-issue desk, lamp and shelves of black folders. On the first floor, where the big bosses presumably reside, the lighting is softer, and there's some serious art on the walls: culture clearly makes a suitable background accompaniment to the agreeable business of amassing millions.

One was put in mind of this by an inadvertently revealing paragraph in the programme to The City Sings: "the Deloitte choir draws together Partners and staff from across the firm", in which upper and lower case act as a firm reminder of the City's social divide. But the Barbican boss Nick Kenyon's excellent project was a drawing-together on a much grander scale: choirs and an orchestra composed of bankers and accountants would share the stage with choirs from state schools on the far less wealthy fringes of the City.

Things kicked off with the massed voices of Deloitte, KPMG, Morgan Stanley, PricewaterhouseCoopers and UBS – the last-named company already a noted sponsor of youth music – and what could be a more fitting starter than Handel's "Zadok the Priest"? The UBS Orchestra was a bit on the ragged side, but the voices swelled satisfyingly. John Rutter's down-home "For the Beauty of the Earth" led on to a heartfelt rendition of five spirituals from Tippett's A Child of Our Time, and we wound up with the "Hallelujah" chorus plus Elgar's Pomp and Circumstance No 1.

Then, after some dazzling a cappella pyrotechnics from the BBC Singers, all the countries of the world suddenly appeared on stage. Children from three primary schools sang "Oranges and Lemons" and "London's Burning" in accurate polyphony; some cool cats from Morpeth comprehensive got the hall clapping along with "Lean on Me"; and the choir of Bridge Academy did their bit to dissipate the suspicion that many people seem to have about such Blairite institutions with a touching song from The Clash in memory of a recently deceased music teacher.

Finally, young and old, rich and poor sang harmoniously together: musical gesture-politics doesn't come more charming.