BBC National Orchestra of Wales, St David's Hall, Cardiff

How much do you know about centaurs? Probably you know they are horses below the withers, human above. But did you know they were heavy drinkers who once got out of hand at the wedding of the King of the Lapiths, tried to rape the bride and got beaten up for their pains?

This fight is the Centauromachy of Simon Holt’s new work for the BBC NOW, whose Composer-in-Association he is. From the title, I expected some rough-housing, perhaps even a corpse or two, certainly a few ASBOs. But it turns out that Holt quite likes centaurs and is intrigued by the musical possibilities of their double nature – their human cleverness and equine physicality (or is it the other way round?).

His favourite centaur of all is Chiron, their King, who was an intelligent beast and skilled at medicine, though probably not a good surgeon. Of the five movements in Centauromachy, two are about Chiron, one trance-like, the other elegiac. The fight itself is a mere episode, and only briefly violent. But the core of the work is the centaurs’ double nature, which is perhaps why Holt has written it as a double concerto, for the unlikely pairing of clarinet (Robert Plane) and flügelhorn (the trumpeter Philippe Schartz), though without allocating one or other nature to this or that instrument, nature being rarely so simple.

Like Birtwistle, from whom he learnt a lot in the distant past, Holt is a soft-spoken Lancastrian with a taste for sharp, edgy sounds and a brilliant yet fastidious ear. Centauromachy is dominated by the interplay of its solo instruments, sometimes trading extravagant roulades, sometimes interweaving delicate oscillations, always making intricate duo patterns that suggest a playful intellect much more than a bellicose temper. He clearly loves the feel of instrumental sonority. As in his recent violin concerto, Witness to a Snow Miracle, he starts out with solo sound, and never really relinquishes it. His orchestra, too, is rich in individual sonic moments, usually for wind instruments, nearly always strikingly effective. But there are also dense, beautifully imagined chords, notably in the third movement, “A Centaur Glimpsed Through Trees”, an image that suggests Magritte and perhaps Debussy, whose genius for mixing sights and sounds I’m sure Holt admires and has studied.

François-Xavier Roth conducted a highly persuasive performance, with brilliantly adept and just sufficiently theatrical playing by the two soloists, both of them NOW principals. Only two things worried me. How are harp and celesta, whose sounds decay so quickly, meant to sustain the long chords Holt gives them, sometimes on their own? And what happened to the centaurs? No sign of any clip-clopping, and only the occasional whinny – from a horse with a human mouth.

Whatever his classical zoology, though, after Holt one listened to Sibelius’s Second Symphony with fresh ears. For all its smooth D-major tonality, it’s an intriguingly fragmented music, bits of theme popping up all over the orchestra, and no section holding the stage for more than a few beats. Roth made much of this feature, pulling out the individual sounds and sometimes exaggerating the contrasts – once or twice perhaps a shade too much; the wonderfully extreme pianissimo of the strings in the second theme of the Andante slightly spoilt by a rough flute and bassoon entry. But mostly these gradients worked well, and Roth used tempo changes cleverly to keep the discourse intact, especially in the finale, a movement that can seem over-inflated but was here kept neatly and athletically to scale. And how well this orchestra now plays: character, precision, and no trace of chromium-plating.

• The concert will be broadcast on Radio 3's Performance on 3 on 16 November at 7pm
• BBC NOW's next concert in the St David's Hall is on 2 December
• Find out more about Simon Holt on his webpage