Looking at the schematic it looks like the second chip does barely anything - is it there just to bump up the level a bit? If I was to build it with just the one IC would it be a bit quiet?
Maybe they wanted a buffer and there was one OA left to use, so why not... and the difference between using a single OA and a double OA doesn't seem to change much in terms of price/design.
It doesn't seem like much, but depending on the HIGH and MID settings, the signal level after IC2.2 changes. I think IC2.1 can be treated as a gain recovery stage.
