Here’s a thing called Mid/Side Processing that offers a lot of flexibility when it comes to making adjustments to the spacialization of a mix or master.
In short, a boosted Mid channel produces a more centered sound, while a pumped up Side channel would give a wider sound to the mix.
The sum of the Left and Right channels is called the Mid. The Side channel is encoded by phase reversing the Right channel and merged with the Left channel. (The phase cancellation will drop the center and only carry the stereo information.)
Audio In Left > Audio Out Mid
Audio In Right > Audio Out Mid
Audio In Left > Audio Out Side
Audio In Right (reversed) > Audio Out Side
Route the Mid and Side (mono) channels differently through two separate processes with EQs, compressors and shit. Then decode the Mid and Side channels back to a regular stereo pair.
Audio In Mid > Audio Out Left
Audio In Side > Audio Out Left
Audio In Mid > Audio Out Right
Audio In Side (reversed) > Audio Out Right
In general, subtle Mid/Side processing is favorable due to phase shifts and imbalance issues which might occur on higher settings.
Remember that it’s possible to automate the Mid/Side processing to work during selected parts of the song, or to use it as a master bus effect (running throughout the song). E.g. if the mix is muddy, shelf the low frequencies in the Side channel.