While Dolby Labs has soaked up much of the benefits for reintroducing multichannel sound into the consumer theater, the fact of the matter is that recordings with a greater than stereophonic soundfield were first introduced into the market in the early seventies with quadraphonic sound. There was discrete quadraphonic, four separate channels, which was made available on reel-to-reel and eight-track. There also was an "SQ" format, which was used for vinyl, in which the two additional channels were matrixed into the stereo channels in a manner not too dissimilar from Dolby Pro-Logic Surround.
There was a brief flirtation with the format, and quite a few albums were produced in with quad mixes, but it never really caught on. Recently, one of the things that record companies have been doing is making 5.1 remixes of the original quad releases on DVD-A and SACD. Mike Oldfield's Tubular Bells and Pink Floyd's Dark Side of the Moon are examples of this practice. Pink Floyd's follow-up to Dark Side of the Moon, Wish You Were Here, was also issued in a quad mix.
I recieved a DVD-R with a bunch of stuff on it from a friend of mine. One of these was an .iso file (CD image) with the cryptic legend "(DTS) - PF_WYWH." Once burned onto a CD, however, I found that it was the original discrete quad mix of Wish You Were Here presented in DTS. Nothing comes out of the center channel and the .1 subwoofer channel is hotter than a motherfucker, but once one compensates for the overwhelming bass, the experience of listening to it is very different than the stereo mix. The CD sounds monaural by comparison.
While I had often felt that Wish You Were Here sounded a bit muddy, I am willing to say that this may not necessarily be because of the sonics, but because the mix was so detailed that it was difficult to separate out the sounds. This is not an issue with the quad mix, which has an extremely wide soundfield and a very aggressive presence all around. The sound effects that are so prevalant in a Pink Floyd album literally surrounds the listener.
The effect was quite mind-blowing to myself and Raz the other night when we listened to it. I had previewed the disc briefly but was unable to listen to it all the way through until he came over. His response was that he felt that he had never heard the record before.
I understand that there is going to be an SACD 5.1 release later in the year.