Multiband X6 - Troubleshooting Masters
If you are mastering and don't have access to the original mix you can make some surprisingly surgical changes to the mix with a good multi-band compressor. Here we tighten up the snare drum so it has a shorter attack and sits tidily in the mix without dramatically changing the rest of the track.
See https://deviousmachines.com/product/x6 for more information.