Exterior of Montreal's proposed new concert hall, designed by Diamond + Schmitt. (SNC-Lavalin)

Montreal's new symphony concert hall will be a private-public partnership under a $266-million agreement signed Thursday.

Premier Jean Charest unveiled the design, created by architects Diamond + Schmitt, at a ceremony on the site in downtown Montreal.

Charest defended the decision to create a public-private partnership, saying it is better for the taxpayer.

"If there are cost overruns, it is the private contractor who will have to cover them," he said, speaking in French. "There are incentives for the private sector partner to do that wherever necessary."

Interior of Montreal's new concert hall. (SNC-Lavalin)

The 2,100-seat concert hall will be slightly smaller than the Salle Wilfrid-Pelletier where Orchestre Symphonique de Montréal now plays.

The stage area incorporates a pipe organ and has room for 120 musicians and 200 singers

Under a partnership with the province, the Ovation Groupe, owned by SNC-Lavalin, will design, build, finance and operate the concert hall for 30 years.

The Quebec company is working with Diamond & Schmitt Architects, which designed the Four Seasons Performing Arts Centre in Toronto.

The design unveiled Thursday has a similar boxy style, with glass-fronted lobbies so musical patrons can see the streetscape, and be seen from outside, at intermission.

There is a lot of wood on the interior, including 9,000 sq. m of Quebec beech.

The acoustics have been designed by Russell Johnson of Artec Ltd., the acoustics genius behind some of the world's top performing venues. It was the last project he did before he died.

OSM music director Kent Nagano greeted the new design with enthusiasm, saying it would be among the top concert halls in the world.

Salle Wilfrid-Pelletier, where the symphony has performed since 1963, is often criticized as overly large and lacking the fine acoustics needed for a symphony.

Previous provincial governments, including the Parti Québécois have promised to build a new concert hall, but those plans never came to fruition.

Former premier Lucien Bouchard, now chairman of the board of directors of the OSM, was among the guests as the design was unveiled.

Work crews have already started to demolish part of the underground parking lot on the northeast side of Place Des Arts to make way for the new building which will measure about 19,000 sq. m.