It's wild to see that multi-multi-mike arrangement there. I was a student at New England Conservatory in the late 1960s and early 70s, and went to concerts of the BSO rather often. They were miked by WGBH-FM with four Neumann omnis (KM 83, which are diffuse-field equalized) that hung down from the main ceiling. The main L and R mikes were placed about six feet behind the conductor's podium, and two others toward the back of the hall picked up ambience. That was it!
I assume that the treble was pulled down at least a little somewhere along the line, since those mikes typically sound hard/harsh when used at ordinary miking distances if that isn't done, and the broadcasts sounded very well balanced.