Music in the mill.

This concert hall has been made out of an old paper mill in a way that enhances the existing spaces while inserting a completely different kind of volume.

Norrkoping was made by the Thirty Years War, when Gustavus Adolphus encouraged the Walloon industrialist Louis de Geer to set up mills to provide the Swedish armies with small arms and uniforms. The works were powered by the Motala river, which at this point rushes into a fjord that joins the Baltic southwest of Stockholm. It became one of the longest industrial riverbanks in Europe, but as in so many other such places, most of the mills have become redundant as technology has changed. Yet the buildings themselves are fine, and indeed make up the character of the city, being scheduled as national monuments.

They are now being altered to accommodate the arts and scholarship. One of the most important and striking changes is to the old paper mill, which Lund & Valentin have changed into the Louis de Geer Kultur och Kongress Centrum. The primary objective is to provide a concert hall for the city's symphony orchestra and an audience of 1300 people. But, as its name suggests, the place is intended to cater for other functions as well.

The horse-shoe shaped auditorium has been cut into the main body of the building. From here, a long thin wing runs out to the east, where it connects to two of the main spaces in the centre of the town, Gamla Torg (old marketplace) and Stromplan (river square). The end of the wing has been carved away to form a dignified double-height porch that welcomes visitors from the town. From the porch, you go through a glass wall to the long foyer that runs along the river. On the other side, a row of office and conference rooms is supported at the upper level on a lightweight steel structure and clad in smooth steel panels. Below, on the entrance level, is a long cloakroom (very necessary in the winters at such a latitude).

Yet this is not a tedious or utilitarian space. You are drawn forward by subtle expansions and contractions of the route towards the promise of the excitements of the big foyer outside the performance space. The cylindrical bulk of the auditorium clad in waxed steel sheets whizzes down through the whole volume. Opposite, a bold double-height polygonal bay of glass and steel has been projected through the mill's old brick wall. Here, people promenade, drink, eat and chat overlooking the river's remarkable man-made waterfalls and the other visitors.

Above this level are the zigzag edges of galleries formed in oak supported on steel I-beams which have their webs drilled out and are hung at their ends by steel tie rods. The ties transfer loads to the new steel roof beams that spread out radially from the drum of the auditorium to the mill's concrete and masonry walls. The variety of forms and levels in the foyers could have been a visual jumble, but a rigorous discipline of colour and material controls the place: the entrance floor is of Oland limestone; the original structure is spatterdashed and ochre lime-washed; the new steel structure is painted dark blue-grey; new concrete walls are distempered 'English red'; the oak floors are left as natural thick wood. Everything is tough, clear, responding to the industrial tectonic of the original building.

Inside the auditorium, there is a much softer feel. The place is daylit by square windows round the top of the drum. It is high and quite little in radius for its seating capacity, with three thin balconies adding to potential audience and reflections. So it is a tall volume that has a melodious series of reverberation times, enhanced by the elegant undulations of the thin birch sound reflector over the orchestra. The dusky plush blue of the seats is carried into the colour of the walls, which become gradually paler as they rise towards the light.

The architects describe the difference between the hard spikiness of the foyers and the soft, rounded smoothness of the auditorium as a tension between 'the universal poles of male and female'. For once the architects' description is right- and their sensual intentions have been amply fulfilled.