I believe I have found a (new?) secret in FEZ's soundtrack, but my visualizer isn't clear enough to capture it 100%.
In FEZ's soundtrack (by Disasterpeace), there are "secrets"- stuff like encoded images. These exist in almost all of the songs, even some of the more atmospheric ones. The game is about a shift in dimensional perspective, like from 2D to 3D and back, and the soundtrack represents that same shift beautifully when you pull up a spectrogram.
Every note is deliberate, in either creating an emotion or image, or even just setting up the rest of the song. White/blurry noise is used to create a sense of space, while mirrored sounds (high-low frequency, like a guitar playing the opposite notes, ascending instead of descending) give a sense of either spookiness or The Ancient Ones (the space squids that mastered the fourth dimension or whatever). Every. Single. Track... has either a secret, is atmospheric for the hell of it, every note deliberate. Disasterpeace did a good job on not making any "throwaway" tracks.
So while messing with setting up a spectrogram for streaming, I remembered the FEZ soundtrack existed, and had a listen to my favorites... and saw something regular. Very regular. HORIZONTALLY, not just the usual vertical of drums or shifting horizontal lines/planes of synths. Tweaking the settings, I got the best screencap I possibly could, but as you can plainly see without the context of the game, it's too blurry to properly see anything besides the telltale grid and tiny lines within, juuuust clear enough to recognize a few, but not enough to read at all.
The song is Sync by Disasterpeace.
This is the original capture:
This is the same image but cropped with the context on top:
This is the FEZ alphabet (for reference), in case you don't know what you're (possibly) looking at: