BBCSO, Bĕlohlávek, Barbican Hall

Nothing stays the same for long in the hypersensitive symphonies of Bohuslav Martinů. A pastoral idyll accelerates to fairground mania before dropping off the merry-go-round, rapture fades in a single bar and victory may be snatched out of the jaws of brutal conflict at the very last second. The Czech exile's rich, compressed works of the 1940s, when he was living in New York and pining for the European scene he loved so dearly, are winning new admirers. A packed Barbican audience for the third in his ideal interpreter Jiři Bĕlohlávek's symphonic cycle with the BBC Symphony Orchestra enthusiastically demonstrated the phenomenon.

It was hardly the sort of programme that usually packs them in, though it deserved to. Belohlávek played to his native strengths in bringing together three very different voices born not long apart and within a small radius. What did they put in the Moravian water that gave rise to Janáček in the rolling hills of Hukvaldy, Korngold in the genial city of Brno and Martinů in a church tower in the small town of Polička?

A lush, romantic first half worked well, even if neither chosen work showed the composer in his most concentrated light. A new suite arranged by Jaroslav Smolka from Janáček's Katya Kabanova highlighted the opera's clash between brute forces of inhumanity and nature on the one hand and fragile love on the other . Those are crystallised in the doom-beating prelude, its tender string and woodwind portrait of the heroine smashed against rattling timpani, played with artistry by  John Chimes, and snarling muted brass.

That works fine in concert, but having only snapshots of frustrated housewife Katya's downward spiral via consummated love into madness and suicide makes one long for more of what is, in any case, a lightning-flash drama. Tender phrases that burgeon and develop in the opera make little sense in isolation, and it was only with the visceral storm - complete with flailing flexatone, that bizarre conjunction of metal bars which I had no idea Janáček used in his score -  and its aftermath that the orchestra alone could really tell the story. Yet Bĕlohlávek knew how to irradiate the tender shafts of light and to hit the climaxes at the right moment.

Then it was time for "smooth classics at 7.30", and thoughtfulness could be checked in at the entrance to Korngold's impossibly easy Violin Concerto. Not that it's simple for the soloist, though grateful in doing what a violin concerto ought to do - providing a steady stream of lyric melodies. Critical jibes at the time of the 1947 premiere - "more corn than gold", "Hollywood concerto" - have a ring of truth about them; the over-repeated big tune of the first movement was written for an Errol Flynn flop, the jolly japes of the finale for his more successful vehicle The Prince and the Pauper.

Yet while a slow movement is superfluous after the leisurely first, it's successful "light-serious" music, and Andrew Haveron approached it with bright charm that was all the more likeable for its easy dovetailing with his orchestral companions. And no wonder, for he's co-leader of the BBC Symphony. The moment that actually brought tears to my eyes was the stamping, cheering accolade of his colleagues in the strings - well deserved after a brilliant and infallibly entertaining finale.

That left plenty of energy for concentrating on Martinů's more complex thoughts in the Fourth Symphony, hardly the sunny inspiration it's been over-simplistically labelled. In bringing the syncopated Moravian-inspired theme of the first movement out of the autumn mists, Bĕlohlávek gently stressed its underlying dance, made its sudden collapse alarming and gave our innards an unexpected flip in the giddying final rise towards the light. The aggressive neon lights in the outer portions of the scherzo made another idiomatic nod at Czech pastoral in its trio all the more affecting; and Bĕlohlávek has all the patience he needs for the slowly evolving argument of the great Largo, mired in homesickness and briefly glowing memories of past happiness.

When I recorded a Radio 3 Building a Library on the Fourth last year, I made the wild claim that this had to be the finest slow movement since the one in Sibelius's Fourth. Belohlávek's masterly argument last night made me even more certain that it's one of the most remarkable in any 20th century symphony. But the clincher has to come in the embattled finale. In his two recordings, Bĕlohlávek lost the momentum in the spirit of '45 by slowing down for the noble chorale. Here he kept the underlying energy charged through to the last, chirpy triumph. Don't miss the rest of this orchestral season's biggest adventure.

Bĕlohlávek conducts the BBC Symphony Orchestra in the remaining three symphonies of his Martinů cycle at the Barbican on 19 March, 17 April and 8 May. Friday's concert is broadcast on Radio 3 on Monday evening (22 February)