As its name suggests, this VST plug-in encodes standard stereo signals to mid/side frequencies. You can then add compressor and EQ effects to each channel, as well as adjust volume and pan settings. The signal is then automatically converted back to left/right stereo for monitoring purposes.
MS EQ COMP can encode standard STEREO (left/right) signal to MS (middle and side) and add EQ and Compressor separately to the middle and side, also edit the volume and pan. The output signal is decoded to STEREO (left/right).
It helps you to correct the stereo image and the sound ambience of the whole music, or add the effects to the signal of the particular instruments (for example, drums, vocal, narration, etc) on a M/S basis.
This is a particularly handy tool for tweaking the ambience of a track and more.