Commissioned by the French Government and Musica Strasbourg.
As the title suggests, Trois rivières is divided into three separate sections. The first part introduces all the instrumental colours used in the piece. The rhythmic aspect is here nearly eliminated, giving room for the timbral scales, colours, resonances, attacks and textures to come to the fore. The instruments come from all members of the percussion family, but unpitched instruments are given a primary role.
The second part adds a rhythmic aspect to the nuances of colour and texture, as an ostinato is developed in markedly varying directions.
The last part is an epilogue, recalling components of the two preceding parts. Here, earlier aspects of the material are reorganised and placed in different relationships to each other.
The voices of the percussionists act together as an extension of the instruments, being used to create either rhythmically free textures or strictly notated rhythms. They are treated instrumentally, combining to create rhythms and timbres. The poem 'La nuit de lune sur le fleuve' (Moonlit night on the river) by the Chinese poet Li Po (701-762) constitutes the material for the voices, which are amplified and further enhanced throughout.