The montage of pictures of Anthony Braxton on the sleeve of his 1969 album B-X0 NO-47A is noteworthy. In one photo he is playing the accordion, his gaze directed to the keyboard with steely concentration. The image stands out because the 75 year-old Chicagoan has, in the intervening years, established himself as one of the greatest of multi-reed players, and also because of the relative scarcity of the aforementioned instrument in what might pass as ‘art music’. Whether Braxton first heard the accordion in the context of a bal musette during his sojourn in Paris with other members of the AACM (Association For The Advancement Of Creative Music) is not known, but over a half-century later its presence in his work seems like more than a twist of fate. Adam Matlock, the accordionist in the sextet, septet and nonet featured on this 11-hour marathon of concerts (in high resolution on one Blu-ray disc) is a revelation. His broad textural range and inventive accenting lend the accordion a vigour and aggression as well as sensitivity and tenderness that make it very relevant to the concept of ‘ZIM’, the newest entry in what Braxton calls language music. His unwavering commitment to concept as well as composition has led him to investigate anything from long sounds to multi-phonics in the past and this latest imagining of continual structural shifts – increasingly faster, slower, brighter or darker – reflects an avowed interest in varying graduation and emphasis in a given musical structure. Tension upon tension and release upon release.

On these two years of live performances there is an emotional substance that remains tied to weighty intellect. The advanced dynamics that come into play when the work hits a peak have a deeply dramatic resonance insofar as the music gets harder and harder, gentler and gentler, more and more chiaroscuro. Ultimately, it is the moments when all of the above entwine to create a delicious ambiguity, pushing to both dark and light, that see Braxton fulfill his ambitions. On ‘Composition 415’ the pulsating croak of his bass clarinet, staccato stabbings of Matlock's accordion and volcanic belch of Dan Peck's tuba produce atmospheres that unsettle and entice, just as some of Baudelaire's best poetry does. There is a true romanticism in Braxton's writing because its meticulous probing can evoke such graphic melancholy as well as ecstasy.

With his changing ensembles Braxton does achieve some startling patchworks that take full advantage of the enormous precision with which the musicians can control legato and presto phrasing, acknowledging and extending Ellington's harmonic flourish all the while introducing a very different sense of rhythm and meter, as if all the fraught sensuality of ‘The Mooche’ were freeze-framed in icy mystery.

The cogs in Braxton's sound machine can grind a little uneasily, as is to be expected when ideas are worked out on the fly, and the big question is whether the engrossing experience of the concerts can really translate to CD. The single Blu-ray disc is certainly an advantage. Hearing ‘Composition 420’, where the liquid swirls of the harps are as mischievous as they are majestic, in high-res stereo suggests that there is a substantial reward for whosoever puts in the time. This uncompromisingly personal work reflects Braxton's ongoing journey towards new sensations in sound. Despite the many paths already explored, he is still managing to find the road less travelled.