'I was recently described as "the world's most adventurous cellist",' wrote Matthew Barley, introducing his week-long residency at London's latest chamber venue, King's Place. 'That was flattering, even if it made me feel a bit like a can of lager.'

The Guildhall- and Moscow-trained cellist brings this sort of thing on himself: why else would his week-long festival be dubbed Xtreme Cello (unless it's his homage to the Parkour and BMX athletes who have for years been the fiercest champions of London's South Bank)? And he did take up Plushmusic's offer to stream his concert over the iPhone mobile platform: a world first that puts live chamber performance in the pocket of anyone stumping up phone's monthly connection fee.

A demotic impulse is all very well (you could watch his recital with jazz pianist Julian Joseph at the back of the bus while drinking the lager...) but what lies beneath the motley? The fact is Barley, far from 'dumbing down', has spent his career to date expanding our ideas of what musical excellence actually is. His pioneering approach to education, community music and orchestral training is world-renowned. 2007 saw his debut on television as the Music Director and presenter of BBC 2's widely acclaimed Classical Star. Stuffed shirts gave him a hard time for placing improvisation at the heart of his training: he gave them short shrift.

The surface eccentricity of Barley's approach is an artefact of perception. Be fair: if the first thing you knew about him was that he liked playing against interactive electronica by Nitin Sawhney and Duncan Bridgeman of 1 Giant Leap, you might be intrigued, but you would hardly be reassured. Barley is happy to address this point head-on: 'I always feel that putting labels on music rather misses the point,' he says. 'It seems more interesting to think in terms of music that dances, or that sings or weeps.' The most ambitious expression of this philosophy to date was his marathon UK tour, On The Road, in 2006 playing 20 recitals and giving 17 workshops in 30 days. The venues ranged from prestigious concert halls to a prison, a school for terminally ill children, and a vegetarian cafe, and included improvisation, core classical repertoire, contemporary music and electronica.

Barley has been ploughing his own furrow for over twenty years now, giving the lie to the addage that to achieve excellence, it's better to concentrate on doing one thing well. Barley's reply: 'I do concentrate on doing one thing – being adventurous. The more serious response would be that to be an artist, you must get to know yourself and find – as Martha Graham puts it – your unique expression.' That journey has toughened as well as broadened his playing. It is, sometimes, exquisitely delicate. But it is not fragile. It communicates precisely. There aren't many virtuosos would get away with performing in a jet-black lycra and velcro motion-capture bodysuit, fewer still who would actively welcome being upstaged in performance by big-screen digital avatars of themselves. That Barley thrives on this kind of audio-visual collaboration – that even Barley's critics thrive on it – is a sure indicator of his intellectual and emotional clarity.

This made Barley an ideal candidate for Plushmusic's world-first iPhone venture. On Sunday 27 September it hardly mattered where you were: Matthew Barley and his friend the jazz pianist Julian Joseph were there in your pocket to entertain you. The recital more than justified the experiment: the critic John Fordham, steeling himself for all manner of musical adventures, praised the men's 'elegantly melodic conversation. Here, the cellist's shimmering bowed sounds and bass-vamp pizzicatos stroked and chased Joseph's grooving chord patterns, double-time jazz variations and pushing swing.' The evening's programme – a series of imaginative improvisations and arrangements – included material from Joseph and Barley's new Signum Records release, Dance of the Three Legged Elephants. The kind and quality of Julian Joseph's contribution was distilled to near-perfection in the duo's violin/piano duet Pièce en Forme de Habanera: a faithful account of Ravel's Spanish-tinged original that bloomed into a heated interchange of eddying cello chords and urgent, flamenco-like piano figures. Joseph describes the inclusion of Ravel's Pièce en Forme de Habenera as 'completing the picture' of the relationship the men have forged between the classical sensibility and the improvised jazz response.

It's unlikely that anyone in the audience expected anything less: Julian Joseph – a virtuoso pianist, bandleader, composer, arranger and broadcaster (his weekly radio show, 'Jazz Legends' for BBC Radio 3, ran for six seasons) – Joseph needs little introduction. He was the first jazz musician to be invited to give a series of all-acoustic concerts at London's most prestigious classical venue, the Wigmore Hall. He has recorded duets by Milhaud, Stravinsky and Poulenc with Brazilian pianist Marcelo Bratke, combining them with his own arrangements of music by Duke Ellington, Chick Corea and Bill Evans, and collaborated with concert violinist Viktoria Mullova on her fusion project Through the Looking Glass. At the same time, Joseph's own classically-oriented work never ventures too far away from his jazz focus, building on the legacy of Duke Ellington, Gil Evans, Herbie Hancock and Jaco Pastorius.

Vika, originally written for Barley's wife, Russian violinist Viktoria Mullova, is a gorgeous, expansive melody with an 8/8 latin feel pulsing beneath. There is something yearningly European in the passionate cello tune, as well as echoes of Chick Corea in the harmonies and piano lines of the solo section.

Resolution, begins with an improvised exchange of dark piano chords against softly whistling cello squeals – an unlikely avenue into John McLaughlin's 1970s Mahavishnu Orchestra classic. But this, like the way Joseph's own slyly displaced blues tips so effortlessly into foot-stomping be-bop, is surely the point: music's intellectual credentials rest on the shifting sands of emotional response.

Barley and Joseph's argument seems to be this: the foundations must not hold. This is not political correctness. This is not 'fusion'. This is, quite simply, how music is made, and made great.