MUSIC / Knocking on wood: Robert Maycock on the BBC Welsh Symphony Orchestra led by Tadaaki Otaka at the Proms

SWITCHING ON Radio 3 midway through Tuesday evening, I heard something unknown by Mahler. The breadth, romantic feeling and incisive sense of purpose all suggested it, at least. Only a familiar wisp of theme betrayed that things were quietly gearing up for the slow-movement climax in Walton's Symphony No 1, and that this was indeed the Prom relay.

The BBC Welsh Symphony Orchestra was living up to its emergence as one of the season's star turns, with powerful strings and an intelligence in the conducting of Tadaaki Otaka that faced the 'problem' of the symphony's finale head- on. So it's too formal and rhetorical an ending for the violent adventures that precede it? Try broadening and intensifying the slow movement - heated drama instead of English idyll. Then tighten up on the Crown Imperial-style tub-thumping, and suddenly the music's proportions make more sense.

It really was Mahler from the same orchestra the next night, and another symphony with a weight problem. Does the Scherzo of the Sixth go before the Andante or after? Evidence for what the composer wanted is ambiguous. Otaka put it before, and conducted it as if to argue the opposite case, at much the same pulse as the long opening movement.

This didn't only labour the obvious kinship between the two - the Scherzo like a parody - but left a sense of being cornered by a haranguing bore. First there's 25 minutes non-stop, and then he starts up all over again: the old image of Mahler that is supposed to have gone for good.

Live in the hall, the orchestra was showing that the previous night's microphones could not have lied. It delivered the weight of violin tone that could cut through a wall of sound. Otaka made the most of the Scherzo's occasional pace changes, and found a delicious languid poise for the slow waltz episode. The first movement had shown steady purpose, setting out as the start of an evening-length symphony rather than digging in right away with the double-basses in case you miss the irony of the march music. It's a pity the off-stage cowbells seemed to be halfway across Hyde Park, but there were plenty of successful subtleties, and a lovely piece of timing in the hold-back at the exuberant peak.

When the Andante did arrive, Otaka again took the broad and warm view. Its long- drawn climax wasn't the usual desperate rush of emotion, but sang in strong, sustained phrases. The sure sense of direction held good as the finale surged forward to its crisis, having husbanded enough of the brass's resources to make it tell. Another of Mahler's bits of theatre, the symbolic blows of fate, done with a slammed wooden frame, sounded like a trapdoor snapping shut and looked like a dismissive kick. Yet the absence of the optional third blow was a positive feature, and not only for acoustic reasons. Instead of bringing annihilation, the end left a door ajar.

Otaka can make a British orchestra play with real tonal intensity and not sound strained. The preparation apparently lacked nothing. It's hard to pin down why the experience missed something vital. There wasn't a spontaneous feeling, but then neither was there when Lorin Maazel and the Pittsburgh Symphony Orchestra devastated Symphony Hall in Birmingham with the same symphony last year. The performance went about as far as any can go that doesn't want to tell you it's a matter of life and death. Arguably, generous musicality is all you need; it works with Walton. For Mahler it never seems enough.