Editing Stereophonic sound (section)

===Pseudo-stereo===
[[File:stereo_widening_example.svg|thumb|192px|A stereo-widening example:<ref>Rick Snoman, [http://google.com/books/edition/Dance_Music_Manual/GRdmAQAAQBAJ ''Dance Music Manual &ndash; Tools, Toys, and Techniques''], 15 October 2013, {{ISBN|9781135964092}}</ref>
{|
|valign="top"|{{nowrap|1.}}||A is a square wave and B is one thrice the frequency.
|-
|valign="top"|2.||Different amounts of A and B are mixed into the {{nowrap|left (L)}} and {{nowrap|right (R)}} channels.
|-
|valign="top"|3.||To widen the stereo effect, a fraction of the opposing channel is subtracted from each channel.
|-
|valign="top"|4.||Normalised results show the signals A and B partly separated.
|}]]
In the course of restoration or remastering of [[monaural|monophonic]] records, various techniques of ''pseudo-stereo'', ''quasi-stereo'', or ''rechanneled stereo'' have been used to create the impression that the sound was originally recorded in stereo. These techniques first involved hardware methods (see [[Duophonic]]) or, more recently, a combination of hardware and software. Multitrack Studio, from Bremmers Audio Design (The Netherlands),<ref>{{cite web |url=http://www.multitrackstudio.com/pseudostereo.php |title=Pseudo-Stereo |publisher=Multitrackstudio.com |access-date=October 17, 2011 |archive-date=October 4, 2011 |archive-url=https://web.archive.org/web/20111004035631/http://www.multitrackstudio.com/pseudostereo.php |url-status=live }}</ref> uses special filters to achieve a pseudo-stereo effect: the ''shelve'' filter directs low frequencies to the left channel and high frequencies to the right channel, and the [[comb filter]] adds a small delay in signal timing between the two channels, a delay barely noticeable by ear,<ref group=note>The comb filter allows range of manipulation between 0 and 100 [[milliseconds]].</ref> but contributing to an effect of ''widening'' original ''flattiness'' of mono recording.<ref>{{Cite web|date=March 31, 2008|title=Hyperprism-DX Stereo Processes—Quasi stereo<!--|chapter=Quasi stereo-->|url=http://ecmc.rochester.edu/ecmc/docs/hyperprism1.5.5/stereo.HTM|archive-url=https://web.archive.org/web/20080331024716/http://ecmc.rochester.edu/ecmc/docs/hyperprism1.5.5/stereo.htm|archive-date=2008-03-31}}</ref><ref>[http://cec.concordia.ca/econtact/8_3/gauthier.html A Review and an Extension of Pseudo-Stereo...] {{webarchive |url=https://web.archive.org/web/20071206065506/http://cec.concordia.ca/econtact/8_3/gauthier.html |date=December 6, 2007 }}</ref>

The special pseudo-stereo circuit{{snd}} invented by Kishii and Noro, from Japan{{snd}} was patented in the United States in 2003,<ref>{{cite web |url=http://www.freepatentsonline.com/6636608.html |title=Pseudo-stereo circuit—Patent 6636608 |publisher=Freepatentsonline.com |date=October 21, 2003 |access-date=October 17, 2011 |archive-date=June 15, 2011 |archive-url=https://web.archive.org/web/20110615003238/http://www.freepatentsonline.com/6636608.html |url-status=live }}</ref> with already previously issued patents for similar devices.<ref>{{cite web |url=http://www.patentstorm.us/patents/5355416/description.html |archive-url=https://web.archive.org/web/20081204103229/http://www.patentstorm.us/patents/5355416/description.html |url-status=dead |archive-date=December 4, 2008 |title=Psycho acoustic pseudo-stereo fold system |publisher=Patentstorm.us |access-date=October 17, 2011 |df=mdy-all }}</ref> Artificial stereo techniques have been used to improve the listening experience of monophonic recordings or to make them more "saleable" in today's market, where people expect stereo. Some critics have expressed concern about the use of these methods.<ref>{{cite magazine|url=http://www.time.com/time/magazine/article/0,9171,871986,00.html |archive-url=https://web.archive.org/web/20080308123110/http://www.time.com/time/magazine/article/0,9171,871986,00.html |url-status=dead |archive-date=March 8, 2008 |title=''Pseudo Stereo'', Time magazine, Jan.&nbsp;20,&nbsp;1961 |magazine=Time  |date=January 20, 1961 |access-date=October 17, 2011}}</ref>