You can see pictures of most of these guys on
Jim Reeves' Vintage Sessions page. Kind of neat to put faces to names and for some of them kinda funny to imagine these straight-laced looking suit-and-tie guys working on some pretty raunchy rock 'n' roll.
Wayne Tarnowski started out working on the original sessions for Chicago II (I think) as an assistant through a work experience program with his university and then continued on from there. When James William Guercio (Chicago's manager) opened Caribou Ranch 1973 he asked Tarnowski if he'd like to move out to Colorado and work as one of the main engineers there based on his work on the Chicago albums II through V at CBS in New York. He went on to engineer all the Chicago albums up until Chicago and Guercio parted ways after Chicago XI, and after that he produced Ted Nugent's Cat Scratch Fever.