We expect to see more and more automated online mastering services popping up, but if you're creating one, how do your differentiate your product from all the others?
In the case of Sound.Tools' Matchering, the USP is that there's a matching function. Rather than just uploading the track that you want to be mastered, you also send a reference track that you want it to sound like. Matchering then promises to match the characteristics of the target and reference tracks, and master the target track with the reference track's "mastering settings".
You can find out more about the process on the Sound.Tools website. Matchering is currently in beta - if you want to try it you can email to request access.