Ambisonic Surround Sound FAQ, version 2.8: Section 3

3. What is surround sound?

First there was mono with the sound emanating from a single "point".

Then there was stereo with directional information spread along a line in front of the listener.

In real life, of course, sound reaches our ears from all directions. Surround sound attempts to improve the realism of the perceived sound by providing information from all directions, not just from in front of the listener.

Surround sound can place you into the middle of an orchestra and there are many pieces of music staged this way. However, in the West, since the eighteenth century most music has been staged with the orchestra in front of the audience. Here, surround sound can be used to reproduce the "acoustic" of the recording venue. This is important because stereo will always be limited to creating the illusion of musicians playing in your living room - a "they are here" illusion. Only if the listener is surrounded with sound can there be any hope of creating the illusion that you have been transported into the recording venue - a "you are there" illusion. When this illusion is successful, surround sound is as big an improvement over stereo as stereo was over mono.