Firstly, on a balmy midsummer's night after Uni students have mostly flown home, how great to see a chamber quartet pack out the venue - Magdalen College Chapel is well met by twilight, as part of Oxford Festival of the Arts' varied strand of events starting at 9pm. Also, as OXUS run a little to the left of the mainstream, the bulk of tonight's music comes from the last 30 years (note to rock readers: this ain't as normal as it should be).

This refreshing area of repertoire and the vitality of subject were what drew me to attend - the idea is that these pieces are the results of conflict experienced or witnessed by the composers. The pearls formed by the friction of creative suppression, political upheaval or even attempted genocide, if you will. Combining performance, recorded music and recorded speech, Steve Reich's Different Trains is tonight's touchstone, taking train journeys as both rhythmic stimuli and jumping-off points for interviews with holocaust survivors. OXUS work us up to this harrowing and transfixing climax, firstly by showing us to an idyll before we can consider its opposite.

Thomas Adès' 'O Albion' comes from his string quartet Arcadiana, a 1994 compendium of evocations of paradise taking inspiration from works by other composers, from myths and paintings. This translucent, gentle movement speaks of a place we cannot see but can imagine. As the audience waits for the concert to begin in what I think is the chapel transept, OXUS accordingly let the wistful harmony and unfolding suspensions of 'O Albion' peal out while hidden from sight in the nave (please do educate me on chapel architecture if I'm wrong about those details). This is as per their brief about "strip[ping] away some of the formality" that somehow still sticks to chamber music performance, and the ensemble does so usefully and respectfully, upending expectations without compromising acoustic presence, and conversationally introducing each piece with the background details that would normally be left to programme notes.

Introducing trial and tremor to this paradise comes Michael Nyman's 'String Quartet No. 3', based on his earlier choral piece Out of the Ruins, from which this evening takes its name. Whereas the first evoked the aftermath of an earthquake, the Quartet celebrates the overthrow of Ceausescu and is fittingly harmonically and rhythmically influenced by Romanian folk music. Nyman's history of gathering folk songs in Romania I didn't know - his method of dramatic phrasal shortenings are more familiar, and effective. I can pick up a small issue with the tuning of a cello string, but more than that see Nyman is undeserving of a reputation as pasticheur, or mere maker of soundtracks - unalloyed with visuals, his work has impact and beauty all its own. We continue with a piece by Shostakovich, another originally for voice - the titular character's lament in his Lady Macbeth of the Mtsensk is translated for strings, and OXUS bring out all its elegiac potential. Although this form removes the opera's 'immoral' text and features its least lascivious music, the knowledge of Stalin's decades-long ban hangs over this performance like a scarily contemporary shadow.

Different Trains is in a class of its own, though; the level of complexity alone must make it a challenge for any ensemble, let alone the vigour needed to maintain its locomotive rhythm. Reich assembled interviewees from his childhood in America, and some who survived the horrors of the camps in World War II - from samples of their speech he grew melodic motifs, developing these across the string forces, recorded and live, and re-harmonising the accompaniment upon each new phrase's arrival. It's akin to trying to play along with birdsong. But OXUS are re-tuned, ready and raring to go; their playing is more alert and precise than I can comprehend, making me want to inspect the score to see how on earth such a feat is directed. The central movement, 'Europe - During the war', carries us deep into the inhumanity of its subject, with siren samples, and marcato gestures illustrating the "flames going up into the sky". The performance is as exhausting as it is effective, becoming especially moving in the final movement, 'After the war', new motifs and material essaying a very necessary and pragmatic optimism that humanity persists through atrocities. I had not heard this piece live before, and for presenting modern chamber music with such a programmatic through-line, for delicacy and stamina, OXUS merit attention, and more than the spirited applause its audience offered.