What if I told you that the part where you say "turn up volume on Windows 10" was actually supposed to simulate turning up your "actual computer volume"?
Originally, we did want the real player (you) to have to eventually turn up your own personal ACTUAL computer volume, but we decided against it because we're not sure if we can generalize everyone who plays ReCursed and what settings their personal volume is at -- we really don't want to risk earraping players by forcing them to up their volume, and then have later sounds be way too loud.
Let's try visualizing laying out all the game dimensions that we see in ReCursed in a single file line and we'll start from the end (dead person) and work our way up. Here's the key: each dimension turns up their OWN system's volume to fill in the passcode for the dimension in FRONT of them.
- We'll call the first dead person we see "P"
- We'll call the minigame player that we've been playing throughout all the puzzles "M"
- We'll call the player that's in the 3D world (free-roam) "F"
- We'll call you, the real player, "R"
Okay, let's lay it out like this:
1. "M" finds dead "P"
2. "F" has to increase their own system's volume control via the Volume Control App (mysterious voices) to fill in the passcode within "M"'s own system
3. "F" finds dead "M"
4. "R" has to increase their own system's volume control via the Windows 10-style slider at the bottom-right corner to fill in the passcode within "F"'s own system (again, the slider being a simulation, you never have to actually increase your own personal volume)
5. "R" finds dead "F"
6. .................
Step 6 is where you claim your friend didn't have to do anything at the end to hear the sounds. Why? Every dimension up to that point had to do something with volume control to hear the voices loud enough, so how come your friend never had to there?
I'll leave the rest to your interpretation :)