It seems Samsung really did complicate things ! Links follows. As they did with High-Res 😞 . Nethertheless thats not a task for the music player.
http://www.androidbeat.com/2018/04/set-custom-ringtone-individual-contacts-galaxy-s9/
The Samsung Galaxy S9 and S9+ are among the best flagship handsets released this year. Packed to the brim with features, they run on Samsung’s latest Experience UI which has been further improved since it first debuted on the Galaxy S8 with new features and enhancements. However, these improvements have ended up making a simple task of setting up a custom ringtone or notification sound on the handset pretty complex.
This is quite ironic since the task of a smartphone first is to make phone calls so all associated functions and features related to it should also be easy to use. It is not like the option to use a custom ringtone or notification sound is not present on the Galaxy S9, it is just unnecessarily complex. But then as they say, where there is will, there is always a way. If you really do want to know how to use custom ringtone sounds on your Galaxy S9, follow the steps below.