When we try to place a signal in the stereo volume or pan, we usually do this by adjusting the relative amplitudes for the left and right channel.

If we want to move the apparent signal source to the left, we increase the volume or adjust pan of the left channels signal and at the same time attenuate the signal for the right channel. This might seem self evident and not even worth to mention, however, there are other means of achieving a similar localization effect – namely, by delaying one channel with respect to the other