Mastering. The final step.
For many musicians the mastering process is strange and almost esoteric. And it's not!
Simply is the final process. The process in which your song or disc is polished to place it on the market. And you have to do it well because the competition is "ruthless".
First I listen carefully to analyze the sound balance of the mix. If there are problems they are solved using techniques like Mid/Side equalization, multiband compression, etc... Then I proceed by giving the final touch with processes such as stereo spacing, peak limiting, dithering, etc...
In the case of a CD, I put the correct order and spaces between songs, all agree to Red Book for further mass production. In the event that your mastering is directed for streaming platforms, I do a special mastering so that your songs are at the appropriate levels for YouTube, Spotify, Itunes or whatever you need.
To do that, I use analog and digital tools. Every music style or mix needs specific techniques.
And above all, the most important, a good pair of ears with many hours of flight!!!