In The Dharma at Big Sur, John Adams's rhapsody for electric violin and orchestra, the composer has achieved the near impossible: a fully worked-through piece, each detail specified, which yet sounds as free as improvisation.

Inspired by Jack Kerouac and West Coast beat culture, this was the high point of the first concert in a mini Adams season, part of the LSO's American Pioneer Series.

If spontaneity is the desire of any composer, that sense of creation with each performance rather than repetition, few achieve it.

European classical music, pinned down by 12 tones - the black and white keys of the piano - resists adventure into what Adams calls the "notes in between", the slides and microtones and blue notes of jazz, rock or non-Western music.

But here the soloist breaks loose and takes flight, bending and keening into a new aural landscape, against which the orchestra remains steadfastly within its regular harness.

This creates an exciting tension as the piece progresses from song-like opening to raw, noisy vortex of a climax.

The transfixing element was the stunning American violinist, Leila Josefowicz, playing a sixstring instrument with low notes like a cello and an upper register more robust than any Strad.

Glittering like a bird of paradise in a minuscule flame-coloured Ungaro sheath, Josefowitz played this fiendish score from memory, infusing it with intensity and controlling acoustic effects with a magic touch of her foot on a pedal.

It's hard to think of many who would risk mastering a new instrument and overcoming fresh professional hazards with such evident relish.

Adams also conducted Slonimsky's Earbox, a party-piece work in more habitual, hard-drive mode and On The Transmigration of Souls, a 9/11 memorial, expertly sung by the London Symphony Chorus and New London Children's Choir.

But the use of big screens for the text, fragmentary recollections of the dead by their love ones, hampered the musical impact, making an uncomfortable document out of a tender elegy.