J.J., I don?t know if you were refering to me but the way I do it is for sure nothing new or a secret. I also think "freqency wise compression" is a little too much but anyway...
At the end of a mix I fire in the stereo compressor of the SSL stereo bus more often than not. Adjust release and attack etc.. But sometimes, with some tempo or music style you get the feeling that the attack of the bass and bassdrum gets kind of washed as the character of the SSL compressor got a kind of pumping, "making everything warm and together" character, IMO.
It can be sometimes hard to achieve the nice colour you get from this compressor AND have the bass and bassdrum still stay tight, especially in electronic and dance.
So in order to get the bass and bassdrum out of the rest, you route all your channels to bus A and the bass and bassdrum to bus B.
Now you copy the same settings you used for the stereo bus compressor, which did not work, to bus A compressor and B compressor, which is possible as you got one for each bus. (A,B,C and stereo bus). Then you turn the stereo bus compressor off. Then you leave the settings, you have made for the stereo bus compressor on the bus A compressor as you liked that before. On the bus B compressor you adjust the threshold until you like the setting for the bass and the bassdrum, adjusting ratio and release I find a little dangerous as my paranoid ears found that they would then kind of fight with the other tracks in a "stereo-compressor-wise-way".
So this would be a very careful way of treating the bass and bassdrum differently in stereo bus compression as the rest of the tracks. Just the threshold would be then a little different as I do not compress the bus too heavily anyway. But many small steps sometimes make a big difference in the end.
Another possibilty is to send the bass and bassdrum straight to the stereo bus and not to bus B. As the stereo bus compressor is turned off, bass and bass drum will stay uncompressed "stereowise" in comparison to the rest of the track.
So you got the settings you liked for the track for all channels expect the bass and bassdrum and so kept the low stuff tighter.
cheers
steveeastend