For Harrison Birtwistle, music in the theatre can never be simply cosmetic; it has to add a dimension to the theatrical experience, to take the drama in a direction that words and gesture cannot; otherwise it is redundant.
That economy and concentration on the dramatic essentials are just as characteristic in Birtwistle's new score for Bacchai as they were 21 years ago, when he worked with Peter Hall on the National's production of Oresteia. But the results this time are very different. In Oresteia, Birtwistle's invention was attuned to Tony Harrison's translation and to its delivery: a network of pulses that established the rates at which couplets were spoken, reflecting the metres in Aeschylus's Greek. The patterning gave that huge epic its dynamic and its coherence, everything was embraced within the labyrinth Birtwistle had created.
That use of basic pulses emerges again in the chorus sections of Bacchai, but more freely and more rhetorically. Defined by percussionists in the ensemble at the back of the Olivier stage, they underpin the speaking of Colin Teevan's prose text, shape it into great paragraphs, often in Birtwistle's favourite verse-and-refrain structures. Sometimes they erupt in choral climaxes of a primeval kind, counterpointed by wailing duets in rhythmic unison for clarinet and oboe. But there are also many parts of the play in which the instrumentalists are silent altogether, and so their contributions elsewhere, perhaps to add a menacing drone to a speech, to decorate a dialogue with descending scale fragments or a seemingly innocuous arabesque,acquire much greater significance; less really does mean more.
For Birtwistle the experience of working on Oresteia fed directly into the composition of his huge, magnificent opera The Mask of Orpheus, and it is tempting to wonder whether the Bacchai will bequeath an equal legacy to the music-theatre pieces he is planning over the next few years. Both of them, intriguingly, have Greek mythological subjects.
In rep until June 12. Box office: 020-7452 3000.
