There are two main endings (Good and Bad) determined by your final choice regarding the cylinders.
The main goal is to find scattered throughout the hotel and its grounds to unlock the secret of the "Great Song". Maid of Sker Switch NSP (eShop)
You must find Gramophones in safe rooms to manually save your progress. Walkthrough & Objectives There are two main endings (Good and Bad)
You can hold your breath to pass enemies silently, but doing it too long causes Thomas to gasp loudly or pass out. Maid of Sker Switch NSP (eShop)
You eventually acquire a Phonic Modulator , a non-lethal sound device that temporarily stuns enemies so you can escape.