It is possible, and even to add custom tracks/sounds as well. Personally, I don't have any experience mixing in sounds and music to games, so I'm not sure if I could get something that would sound right, especially as I often turn down/turn off the music for h-games in the first place for sounding...'wrong'. I know enough to know when it's bad, but not even to know how to make it good, basically. Currently, Inusuku has basic sounds and 'nighttime' music to make the nightcrawling feel more realistic, so while adding to it would be nice, I wouldn't want to destroy the vibe Inusuku has set up in the game. If you have any recommendations, feel free to let me know.