Prom 45, Royal Albert Hall, London<br/>Prom 46, Royal Albert Hall, London<br/>The Emperor of Atlantis, Arcola Theatre, London

A premiere is followed by a little syncopation &ndash; but conservatoires can't teach musicians to swing

Calm, alert and unhurried, Thomas Larcher's Concerto for Violin, Cello and Orchestra (Prom 45) is a space in which to breathe and listen. Nothing is quite as you might expect it to be.

Faint rustlings catch the ear: the rub of a palm on the skin of a drum, the lazy grin of an accordion, the mosquito whine of a bow drawn across metal. Here, where solo violin and cello imitate viols in their elegaic, dove-tailed figures, where lush, dewy choirs of woodwind and brass shimmer and bloom, Larcher has created a unique landscape. Electric zither, accordion, percussion and prepared piano offer a frame within a frame for the violin and cello. Romantic in the radiance of its tutti sections, Baroque in its collegial broken consort and the grave simplicity of the cadences that link its two movements, the work affords no grandstanding, no pyrotechnics: it is chamber music on a symphonic scale.

As the first work in the BBC Scottish Symphony Orchestra's Prom with Ilan Volkov, and the first of two Proms performances given by violinist Viktoria Mullova and cellist Matthew Barley on Thursday, Larcher's new-minted Concerto established a tonal purity and thematic spaciousness that continued in Volkov's unsentimental reading of Bruckner's Fifth Symphony. Led by Laura Samuel, founder member of the Belcea Quartet, the strings breathed into the Schumannesque suspensions and shy pizzicato bass of the opening Adagio. Though the horns sounded edgy, the trombones glowed. The timbre of Stella McCracken's oboe solo was almost Russian in the baleful second movement, the Scherzo hot, giddy and malevolent. The pursuit of serenity is a sweaty business in Bruckner, yet the blaze of the closing movement had a rough, healthful beauty.

Mullova and Barley's musical conversation continued in their late-night session with Julian Joseph, Paul Clarvis and Sam Walton (Prom 46). Tagged to the release of Mullova's latest disc, The Peasant Girl, this was a winsome crossover experiment in the mould of Through the Looking Glass (2001), with numbers by Bratsch and Weather Report arranged, as before, by Barley. As the only member of the band to bend a rhythm with style, Joseph was scandalously under-utilised, while Walton's equal temperament marimba made me long to hear the watery pitch of a cimbalom. Regardless of Mullova's Ukrainian roots, gypsy music suits her no better than it would Anne-Sophie Mutter. But why should it? Of the conservatoire-trained violinists that I've heard play gypsy music, only József Lendvay Jr can do it, and his father is a folk-music legend. Mullova played with dutiful attention to every ersatz off-beat, every just-so quartertone but only came to life in the mordant smears and guttural aphorisms of Kodály's Duo – confident and expressive, at home in the music. Written in Terezin, the concentration camp just a few miles from Prague, Viktor Ullmann's The Emperor of Atlantis is a zeitoper unlike any other: a brittle, sophisticated cabaret, a nostalgic romance, a Chaplinesque satire on a world where Death has gone on strike, a declaration of defiance. It is also a lament for Ullmann himself, Hans Krasa, Pavel Haas, Erwin Schulhoff and the other Czech composers of their generation who were annihilated in the Holocaust, fracturing a tradition that extended back through Janácek and Josef Suk to Dvorák and Smetana.

Designed by Valentina Ricci, Max Hoehn's plucky production in this year's Grimeborn Festival revealed what a challenge Ullmann and his librettist, Peter Kien, set their performers. Ullmann's orchestration was necessarily compromised by circumstance – a bran-tub of string quintet, woodwind, banjo, saxophone, trumpet, piano and snare drum – but wittily blended. He was a gifted pasticheur, darting from sour-sweet dances to opulent love duets, a caustic inversion of the German national anthem, quoting from Suk's Asrael. Had Ullmann made it to America, he could have given Weill and Korngold a run for their money. But only in the final aria for the impotent, lonely, murderous Emperor (Thomas Humphreys) and the closing quartet's Bergian extrapolation of Bach's "Ein feste Burg ist unser Gott" does Ullmann fully show his musical personality.

Smartly conducted by John Murton, with excellent work from percussionist Ollie Taylor, flautist Tom Hancox and double-bassist Georgine McGrath, The Dioneo Players kept the textures light and clean. Ullmann's score calls for more lyricism, vocal heft and better diction than a very young cast could deliver in a difficult acoustic, and Humphreys's attractive baritone faltered under pressure. In the supporting cast, soprano Christiana Petrou soared sweetly in the final quartet, with Osian Gwyn a confident, quick-witted, characterful Loudspeaker.

Grimeborn (020-7503 1646) to 27 Aug

Next Week:

Anna Picard hears the Gustav Mahler Jugendorchester at the Proms

Classical Choice

Glyndebourne comes to the Proms as Ottavio Dantone directs the Orchestra of the Age of Enlightenment in Handel's Rinaldo at the Royal Albert Hall, London (25 Aug). Meanwhile in Edinburgh, Vlaamse Opera stages Nigel Lowery's production of Rossini's Semiramide at the Festival Theatre (from 25 Aug).