Total Immersion: Brett Dean Barbican 18 March 2012

Brett Dean is one of the most accomplished and one of the most highly regarded of contemporary composers, so London audiences could feel justified in complaining they don't hear enough of his music. His opera Bliss has yet to reach the London stage (although it's been to Edinburgh), and his Violin Concerto, which is already six years old and is revered as the finest yet of the 21^st century, hadn't been played in the UK before this evening.

In fact, we haven't been neglected as much as it seems. In one of the talks that made up today's programme, Dean pointed out that the BBC SO has played more of his music than any other orchestra. And this is the second day of events in the capital dedicated to his music in just over a year – the Wigmore Hall hosted a similar event in 2011 – so on balance we've been well supplied. But the sheer quality of his music, the immediate engagement it invites, and the effortless sophistication in every phrase, is dangerously addictive. Even if we have had our share, the BBC SO are to be thanked for indulging us again, and presenting a range of new perspectives on this ever-unpredictable composer's art.

Dean's music is filled with paradoxes. It always feels contemporary, yet there is little in it, technically speaking, that Hindemith would not recognise. It's powerfully expressive, yet fashionably modern, and atmospheric yet detailed in the extreme. Then there is the question of geographical placement. The composer spent 14 years as a viola player in the Berlin Philharmonic before returning to Australia to compose full time. To my ear, his aesthetic succeeds because it combines everything that is best about central European Modernism with all that is good in the Australian vernacular. So you'll find the wide expanses of Peter Sculthorpe in Dean's orchestral scores, but even here the music is constructed with the harmonic and thematic rigour that you might expect from Rihm, say, or even Ligeti.

The events in the BBC SO's 'Total Immersion' day gave plenty of scope for such reflections. The way these events are formatted these days is that the orchestra gives a big concert at the end of the day, with everything preceding it on a much more modest scale. Considering how much this final event must cost, it is little surprise that economies are made elsewhere. Even so, the nine hours of events that led up to this grand conclusion did feel a bit meagre. There was only one other concert of Dean's music, and even that was given by conservatory students. Also on the programme were two interviews with the composer, a concert of student works inspired by him, and a screening of his opera.

There was a strange sense of deja vu at the first event of the day, a discussion between Brett Dean and Tom Service, for it was Service who hosted the interview slot at the Wigmore Brett Dean day last year. To both men's credit, they managed to avoid repeating themselves, and the only aspect of this event that had taken place at the Wigmore last year was Dean picking up his viola and playing his signature piece Intimate Decisions. This really is a masterpiece, a work for a solo instrument of considerable duration that never feels restricted by its diminutive instrumentation. Like all Dean's music, it is also astonishingly hard, but the ease with which he dispatched the complex figurations demonstrated that his musical gifts are not limited to composition.

The lunchtime concert was given by students from the Guildhall School next door under the composer's baton – yes, he conducts too. The student performers played his music competently, but it was at this point in the day that the technical demands became apparent. But one undoubtedly Australian element of Dean's music is the overt confidence it exudes. Even in the more nebulous and atmospheric passages, this music needs to be presented with surety and panache, and while the Guildhall musicians had all the notes under their fingers, there was a certain sense of poise that the whole concert lacked.

There was some great music here though. Polysomnography is all about sleep (and I wonder what his agent and publisher had to say when he announced that theme for his work). Dean's compositional process tends to be a path from the particular to the abstract. So, in this case, he studies the science of sleep – REM, brain activity patterns, that sort of thing – and uses these as his initial inspiration. But the music that results is so abstract and self-sufficient that the title, which invariably references that initial inspiration, seems far too specific. Another recurring theme is the music of earlier composer's and Wolf-Lieder, a work for soprano and ensemble, mixes quotations from Wolf's songs with Dean's own musical reflections on the composer's fate. Beethoven, Brahms and Gesualdo got a similar treatment in the evening concert. All three cases invited admiration for the sheer compositional skill involved in integrating earlier music seamlessly into a contemporary work. But they also raise the question of why the composer would want to do so, a question he struggled to answer when it was put to him in interview. There were one or two standout performances from the students. Jenavieve Moore sang the Wolf settings well, a little underpowered perhaps, but her German was always clearly articulated. Special mention should also go to the bass trombonist,Oliver Yusuf Narcin, who had his work cut out in Wolf-Lieder, but made an excellent job of it.

Dean's opera Bliss, the most high profile among his many successes to date, desperately needs a good quality DVD release to help it reach the corners of the world that have as yet to see it live – including London. Sadly, the video we saw today isn't it. Instead it is a recording of a live ABC television transmission, with only mediocre sound and visual editing done in real time. To add to this, the screening took place in the appropriately named 'Pit', on a makeshift screen and with an audio system that really wasn't up to the job. It was good to finally see the production, having heard it on Radio 3 from Edinburgh last summer, and the piece is clearly a milestone in the history of opera (not just in Australia), but this pretension did it little justice.

It is a shame that in these financially straightened times, the BBC could only stage one orchestral concert for the day, because Brett Dean's use of the orchestra is what really sets him apart from the crowd. Although many aspects of his music are conventional, his orchestration is always radical and unique. The string section, for example, is never used as a single, homogeneous unit, but divided into smaller sections that interact with astonishing subtlety. And when he writes dense textures, the sheer number of notes he gives the strings turns the pages of their music black, visibly so from the auditorium. His experience as a violist has given Dean a strong grasp of the importance of the middle in orchestral textures. So he'll use the flute in its lower range, for example, or the middle register of the horns, as the basis of expansive mezzo forte textures, which retain their timbral focus thanks to this concentration on the middle.

This was no better demonstrated than in the first work, Testament, for 12 violas. The work reflects on Beethoven's Heiligenstadt Testimony, using various sonic intimations of writing with quill, of deafness, and of Beethoven's own music in the form of a quote from a Razumovsky quartet. Few other composers would have the necessary skill, or even the motivation, to write for such an ensemble, but Dean makes the unusual instrumentation into a musical virtue rather than just a problem to be overcome. Sadly, the Barbican's leaden acoustic worked against every texture, deadening whatever resonance there may have been. An interesting piece though, and it was great to see the composer get his viola out again to join the ranks.

The Violin Concerto that followed was, by a considerable margin, the most accomplished and most significant piece on the day's programme. It is a work for large orchestra and a busy soloist, whose job it is to keep up with the dazzling array of orchestral textures. Dean manages to overcome his obsession with the mid-range to write a solo part that sails across the top of the ensemble. As with his writing for orchestral strings, the solo violin part is dense and continuous, and comparisons have rightly been made with the Sibelius in terms of the sheer physical demands it places on the soloist. Renaud Capuçon gave a typically Romantic reading, with lots of swooping portamento and unashamedly wide vibrato. There is plenty of room in this score for that kind of expression, although I suspect that Frank Peter Zimmermann, for whom the work was written, does the piece more favours with his less flamboyant approach. Just one criticism - there is too much to hear. You can spend five minutes marvelling at the orchestral writing (and playing) and completely miss the fact that the soloist has been playing away the whole time, and articulating a solo line of equal beauty. Repeated listing is definitely in order, so the sooner this work returns to the London stage the better.

Carlo, for strings, choir and I think electronics too, is all about Gesualdo. Knowing that he couldn't, and probably wouldn't want to, ape Gesualdo's style, Dean sets up a duality between Gesualdo's music in the choir and his own in the strings. Anybody who feels frustrated by the few musical responses Stravinsky made to Gesualdo (despite his verbal advocacy) might appreciate this work as the piece Stravinsky never wrote. In fact, Ligeti is a more obvious precedent for the string writing, which is as unstable and unsettling as the motets it accompanies.

The last piece on the programme, Fire Music, was the only real disappointment among the many works presented today. For reasons best known to himself, Dean chose to honour two commissions with the same work, one for the concert hall and one for the ballet, but its the ballet that wins. The inspiration here was the bush fires that raged across South Eastern Australia in 2009, so as you might expect, the results are quite colouristic, even expressionistic. Naturally, the orchestration is fabulous, with groups of off-stage brass, percussion and strings giving the audience the feeling that they are sitting right in the middle to the textures. But apart from these orchestral colours, there is little else going on here. The rigorous approach to themes, harmonies and textures that Dean has inherited from the mid-European Modernists is put on hold, and without it his music lacks linear and structural focus. I could imagine it making a great ballet though, but of course the chances of a choreographed version of the work reaching London are as close to zero as makes no odds.