At the 1958 World’s Fair in Brussels, an unprecedented musical event was situated in a specially designed pavilion, sponsored by the Dutch electronics company Philips (which is still making flatscreen TVs and such today). The design of the pavilion was done by the architect Le Corbusier, but was mainly the work of composer/architect Iannis Xenakis.
Inside the structure there were an estimated 350 loudspeakers used to project the sound, with 51 lighting configurations to create a truly immersive experience. The music for the pavilion was written by Edgard Varèse at the request of Le Corbusier, entitled Poème électronique. The piece is still viewed as the classic example of the musique concrète technique and aesthetic. Varèse called this the ‘liberation of sound.’ [Incidentally, in that article, if you look at the paragraph under the heading Music as Art Science you'll see that Varèse's vision of a machine capable of doing super-human things has been realized in the form of any current laptop with basic sequencing software.]
The wiki link for the pavilion is nicely done.
Below I’ve posted a great virtual reconstruction of what the experience would have been like, depicted in two parts. This realization is by Fabio Turcheschi.