A black box is a room for theatre where there is no fixed interior except for lighting and sound systems. Seats and stage platform, if there is one, are all moveable, making the black box theatre a most flexible stage type, as the audience can be placed anywhere in the room. It is common practice to paint every surface in the room black to make for neutrality and to reduce reflections, and this is the origin of the name.

The black box theatre was invented in the last half of the 20th century, the first permanent black boxes being constructed during the 1960s. There was extensive experimentation with very sophisticated versions that included a lot of machinery, ie making the theatres "mechanical-adaptable" - seats swinging in place, stage rising out of the floor etcetera, but these attempts were rarely successful, and today's black boxes are normally fairly simply constructed.

Most black box theatres are small in the sense that they would rarely handle an audience of more than 200, a fact that also has a certain impact on what kind of plays you can see at a black box theatre. The stage type is popular amongst smaller, professional theatres, but major productions that rely on massive audience turnout would normally go for a traditional proscenium, which is the most common type of theatre stage.

For some reason, a lot of black box theatre owners seem to be highly unimaginative when it comes to names, which means there is a multitude of black box theatres worldwide simply called "The Black Box Theatre".

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