(If you were viewing this solution on Xbox One using TA App, I'd recommend to use Internet Explorer instead. Links don't work on TA App as of now.)
SUMMARY:
Unlock all the sound tracks used in this game.
DETAILS:
You can check the tracks you've unlocked in Main Menu - Extra - Library - Music. Most of the sound tracks are unlocked automatically as you play the game towards the true ending. One exception is track 49, which is unlocked by selecting positive at the 1st delusion trigger of chapter 3.
LINKS:
Solution for おっけい In Chaos;Child (found True Route)
Solution for 【情報強者は事件を追う】 In Chaos;Child (basic tips. Won't hurt to read if you haven't)