Duophonic
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Duophonic sound was a trade name for a type of
This was done by splitting the mono signal into two channels, then delaying one channel's signal by means of delay lines and other circuits, i.e. desynchronizing the two channels by fractions of a second, and cutting the bass frequencies in one channel with a high-pass filter, then cutting the treble frequencies in the other channel with a low-pass filter. The result was an artificial stereo effect, without giving the listener the true directional sound characteristics of real stereo. In some cases, the effect was enhanced with reverberation and other technical tricks, sometimes adding stereo echo to mono tracks in an attempt to fool the listener.
Capitol employed this technique in order to increase its inventory of stereo LPs, thus satisfying retailer demand for more stereo content (and helping promote the sale of stereo receivers and turntables). For nearly ten years Capitol used the banner "DUOPHONIC – For Stereo Phonographs Only" to differentiate the Duophonic LPs from its true stereo LPs.
Capitol began using the process in June 1961 and continued its practice into the 1970s. It was used for some of the biggest Capitol releases, including albums by The Beach Boys and Frank Sinatra. Over the years, however, some Duophonic tapes were confused with true stereo recordings in Capitol Records' vaults, and were reissued on CD throughout the 1980s and 1990s. Capitol intentionally reissued some of the Beatles' Duophonic mixes on The Capitol Albums, Volume 1 and The Capitol Albums, Volume 2, in 2004 and 2006, respectively.
On rare occasions some artists deliberately used fake stereo to achieve an intended artistic effect. In such situations artificial stereo was used when certain elements of a mono mix could not be reproduced for a stereo remix. An example is the Beatles' stereo mix of the song "
Other record companies used similar processing of monophonic material to create a stereo effect, but referred to it by other terms, such as RCA Records' "electronically reprocessed stereo" and Columbia Records' "Electronically Re-channeled for Stereo". As with Capitol, Columbia's artificial stereo issues included albums by major artists, such as Miles Davis ('Round About Midnight, CL 949 mono, reissued in stereo as PC 8649).
See also
References
- ^ Brennan, Joseph. "The Usenet Guide to Beatles Recording Variations".
- ^ Yellow Submarine 2009 Remaster Booklet