Out Of Phase Stereo (OOPS)
Encyclopedia
Out Of Phase Stereo is an audio technique which manipulates the phase
of a stereo audio track, to isolate or remove certain components of the stereo mix
. It works on the principle of phase cancellation, in which two identical but inverted waveforms summed together will "cancel the other out".
of one speaker or signal lead. It can also be performed using digital audio
software by inverting one of the channels of a stereo audio waveform, and then summing both channels together to create a single mono channel. Those components common to both channels (that is, those sounds that are recorded as a mono track, and duplicated identically onto both channels) will be phase cancelled, leaving only those sounds that differ between channels.
tracks, or generate surround channels from a stereo source, such as in Dolby Pro Logic
. It has also been used in the recording process to include tracks that were only audible once an OOPS technique was applied. This feature can be observed in several of the Beatles
' stereo albums. Australian band Cinema Prague
recorded a single track Meldatype that contained two songs played simultaneously, one of which was only audible after an OOPS technique was applied.
Phase
-In physics:*Phase , a physically distinctive form of a substance, such as the solid, liquid, and gaseous states of ordinary matter**Phase transition is the transformation of a thermodynamic system from one phase to another*Phase...
of a stereo audio track, to isolate or remove certain components of the stereo mix
Stereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
. It works on the principle of phase cancellation, in which two identical but inverted waveforms summed together will "cancel the other out".
Phase-cancelling technique
In practice, the OOPS technique can be performed by inverting the polarityPolarity
In physics, polarity is a description of an attribute, typically a binary attribute , or a vector . For example:* An electric charge has a polarity of either positive or negative....
of one speaker or signal lead. It can also be performed using digital audio
Digital audio
Digital audio is sound reproduction using pulse-code modulation and digital signals. Digital audio systems include analog-to-digital conversion , digital-to-analog conversion , digital storage, processing and transmission components...
software by inverting one of the channels of a stereo audio waveform, and then summing both channels together to create a single mono channel. Those components common to both channels (that is, those sounds that are recorded as a mono track, and duplicated identically onto both channels) will be phase cancelled, leaving only those sounds that differ between channels.
Applications in music
This technique has been previously used to eliminate vocals in a stereo track (as vocals tend to be panned centre) to create crude karaokeKaraoke
is a form of interactive entertainment or video game in which amateur singers sing along with recorded music using a microphone and public address system. The music is typically a well-known pop song minus the lead vocal. Lyrics are usually displayed on a video screen, along with a moving symbol,...
tracks, or generate surround channels from a stereo source, such as in Dolby Pro Logic
Dolby Pro Logic
Dolby Pro Logic is a surround sound processing technology developed by Dolby Laboratories, designed to decode soundtracks encoded with Dolby Surround. Dolby Stereo was originally developed by Dolby in 1976 for analog cinema sound systems...
. It has also been used in the recording process to include tracks that were only audible once an OOPS technique was applied. This feature can be observed in several of the Beatles
The Beatles
The Beatles were an English rock band, active throughout the 1960s and one of the most commercially successful and critically acclaimed acts in the history of popular music. Formed in Liverpool, by 1962 the group consisted of John Lennon , Paul McCartney , George Harrison and Ringo Starr...
' stereo albums. Australian band Cinema Prague
Cinema Prague
Cinema Prague are an Australian funk metal band, formed in Perth in 1986.Cinema Prague are a band who's combination of humour, funk, thrash and Zappa-esque arrangements made them one of the most entertaining and musically dexterous bands to ever come from Perth...
recorded a single track Meldatype that contained two songs played simultaneously, one of which was only audible after an OOPS technique was applied.