[1] When a sine wave is mixed with one of identical frequency but opposite amplitude (ie: of an inverse polarity), the combined result is silence.
[3] In practice, the OOPS technique can be performed by inverting the polarity of one speaker or signal lead.
This technique has been previously used to eliminate vocals in a stereo track (as vocals tend to be panned centre) to create crude karaoke tracks, or generate surround channels from a stereo source, such as in Dolby Pro Logic.
[5] It has also been used in the recording process to include tracks that were only audible once an OOPS technique was applied.
[6] 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.