Concept: Survival horror game where your primary tool for managing the danger is a portable cassette player/recorder that you can use to make a variety of sounds to trick the monsters. Reproduce the cry of a bigger, scarier monster to drive them away, or leave your walkman playing somewhere to act as a decoy. Later in the game, you obtain a cassette with the bone hurting note being played on it, which can be weaponized.
Cassettes in this game would be fully systemic. You can record sounds from the world onto them. You can find tape decks in the world that you can use to duplicate useful tapes. Blank cassettes are a resource. If you leave a cassette playing in a tape deck somewhere as a decoy to attract monsters away from you, you're essentially spending the cassette as a resource. You can even 'program' events and behaviors by recording different things onto different sections of a tape.
If you are injured, the way you heal is of course by listening to a perfect mix tape that your best friend (who died to the Horrors early in the game) gave you. Doing so of course can attract attention from monsters until you find a pair of headphones later in the game. It is totally possible to overwrite or erase this precious mix tape, permanently throwing away the ability to heal.
