I wasn’t quite sure what to expect from the Kronos Quartet’s ‘Musical Meditation on the Anniversary of 9/11’, the centrepiece of their week-long Barbican residency. Especially, I must confess, when I learned that the recital would feature a children’s choir. There was a chance, I thought, that this would be taking things slightly too far. Would this be the moment when the Kronos’ famed rock-star approach to concerts slipped into overblown self-parody? Would this be their Zoo tour?

Thankfully, it wasn’t. At all. The New London Children's Choir sang beautifully in Aulis Sallinen’s Winter Was Hard, and the effect was sentimental but still tasteful. It was a fitting climax to a thoughtful, intelligent and spectacular evening of music both about and not about 9/11. The Kronos’ carefully-drawn programme was a truly appropriate ‘meditation’ on this event, which touched something profound about the way it fits into the contemporary Western mindset.

Loosely arranged in three parts, each with a broad geographical focus, this was very much a programme-as-artwork sort of recital, but it didn't draw out a narrative so much as move gracefully about different areas and ideas. It frequently touched on the concert’s stated theme only by loose association or in fact this theme’s absence. The quartet performed on a set littered with pieces of metal, giving a post-disaster air to the whole evening. But the first set of music, which moved sporadically around Asia, was profoundly apolitical.

In this section Kronos performed four pieces of composed and traditional Asian music, with their characteristic intensity and sincerity. Lev ‘Ljova’ Zhurbin’s arrangement of the Iraqi folk song ‘Oh Mother, the Handsome Man Tortures Me’ was vivacious and rhythmically brilliant. The quartet’s approximation of traditional Asian musical styles was amazingly convincing, and without actually claiming to be Iraqi folk musicians, Kronos conveyed (‘captured’ seems wrong) the spirit of this music with a zealous fidelity. The same can be said of the Iranin and Indian music played, and just as beautiful was the opening rendition of Uzbek composer Dmitri Yanov-Yanovsky’s Awakening, an eerie, twiddly soundscape evoking sparse central-Asian terrain.

The focus then moved – via a slightly perplexing arrangement of Armenia by German industrial band Einstürzende Neubauten, which involved hitting metal things, using a circular saw onstage, and grimly muttering German poetry – towards North America. First was John Oswald’s Spectre, which began organically out of the group tuning, and built up a dense noise collage in collaboration with a large amount of overlaid pre-recorded material. The live group eventually stopped playing altogether, instead silently waving their arms in conjunction with the continuing crescendo. A remarkable effect-piece, its odd, literal vacuity set the pace for the next piece as well.

Michael Gordon’s The Sad Park combines the live string quartet with recordings of young children’s recollections of the events of 9/11. Kronos played Parts 1 and 4 on Thursday, respectively titled ‘two evil planes broke in little pieces and fire came’ and ‘and all the persons that were in the airplane died’. In Part 1, the spoken phrase was looped and gradually slowed down, to the accompaniment of a static, light, bouncy score for the quartet, pointedly unengaged and perfunctory. Part 4, in which the voice was manipulated beyond comprehensibility, adopted an aggressive rock style, perhaps attempting vainly to forget the words, which remained inescapable despite their absence.

This piece – which lacked a centre not just in that the middle movements were omitted – pointed towards the impossibility of really knowing 9/11. Gordon touched on the horrible objectivity of the day’s events, the sense in which they are almost beyond meaningful interpretation. The programme subsequently began a gradual movement towards a certain introspective acceptance: perhaps the only appropriate thing to do artistically.

The final section of the concert had a universalist theme, explicitly stated in Terry Riley’s One Earth, One People, One Love and further elaborated on through a touching and very much neutral Swedish folk song, and Sallinen’s tender Winter Was Hard. The closing piece, an arrangement of Vladimir Martynov’s The Beatitudes, was tender and harmonically rich, austere in a reassuring sort of way.

I find it essentially impossible to imagine how this music, all new to me, would have sounded in a different programmatic context, or played by a different quartet. Such was the sensitivity of the concert’s structure, and such is the uniqueness of Kronos’ utter, palpable belief in the works they commission and perform. It is not a majority of ‘musical meditations’ on tragedies on the scale of 9/11 that are unambiguously intelligent and successful. Kronos can only be commended for a completely absorbing, wonderfully pensive programme.