Buried deep within its settings, the Galaxy S9 has a few audio features that I find enhances music when I use headphones.
The Dolby Atmos feature is like an overall booster of music to make it sound a little more dynamic and exciting.
The UHQ upscaler can give a sound quality boost to your music, even if it's artificial.
The Tube Amp Pro setting gives music a warmer, rounder sound that's similar to classic tube amplifiers.
There's also a Concert Hall setting that basically gives an echo boost to your music, but I don't like it very much. Still, it's there for Galaxy S9 owners to try.