Back in the day, we just took a channel differential (L minus R) with one channel high passed so the difference didn't have all the bass eliminated. Tons of re

Back in the day, we just took a channel differential (L minus R) with one channel high passed so the difference didn't have all the bass eliminated. Tons of reasons it sucked: stereo reverb on vocals wouldn't cancel out, other instruments panned dead center (or at least highly correlated) would cancel out along with the vocal, and early MP3 encoders often sounded better in "joint stereo" or "intensity stereo" mode (assuming low/mid bitrates) which very reasonably gave more bits to the center and fewer bits to the sides, so the differential sounded like hot garbage. Exciting to see that this technique has been replaced with ML.