I have an update for #173. It turns out the glasses do NOT unlock it, rather, the piano in the left room is Directly marked with Varible #2751, which is named 壁紙フラグ 173. when tossed into Google translate, it becomes "Wallpaper flag 173". I ran 5 trials with this info, and was given 173 all 5 times. Please update this info.
File:Proof of 173.png
Here we have the full proof of my finding.