Tried this out and it's actually pretty good.

https://www.landr.com/en

You just upload the track and it's mastered and sent back. Tried one of my son's tracks and it was more musical and professional sounding. Not sure exactly what they run tracks through, but sounds almost like some analog mixer/tube EQ or something, and just a bit "airy" (mastering reverb perhaps).

Worth checking out. I heard something play on Soundcloud that sounded great and looked up Landr just bc I thought maybe it was a studio they used or something. I don't do that often unless I like the results.

https://soundcloud.com/tltd/asylum-instrumental-by-terramorphous-landr-mastered

I had one after this that got the "too loud" warning, and don't remember having it on this one, but always good to leave the volume down a bit, maybe even turn off any master limiting/EQing too. This passed, but was already mastered to my son's taste when I sumbitted it. There's a sweet high mid clarity now that I like and not so many things you have to selectively hone in on to hear.

All Eleven Rack & Steven Slate Drums, Fabfilter Twin synths. Ownhammer impulses on the rhtyhms but leads are all 11R patches.

ORIGINAL: https://soundcloud.com/neptune-boy/asylum-instrumental

Around 2 minutes, the difference in the sythns and smooth transition back to heavier sounds is a definite improvement.

I guess if you can come close already, you will benefit, but I've read conflicting reviews none of which had any real before/after examples. So it's something to try for yourself. You get the wav for free, and pay if you want the mp3 for iTunes.