 In practice, the OOPS technique can be performed by inverting the polarity 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.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.