Sorry. Check your facts, bud. Only to a USB drive not on the HDD of the PS4 itself, which is what games would need to play "custom" music like what you are speaking of.
http://blog.us.playstation.com/2014/...tation.Blog%29
"
USB Music Player: PS4 owners can play their own music in the background while playing a game using USB Music Player*. After inserting a USB stick loaded with music into the PS4, a new option for USB Music Player will appear. Supported filename extensions include MP3, MP4, M4A, and 3GP."