[Nils Jacob Holt Hanssen]

But intuitively I believe that there are certain natural principles of aestetics like the golden ratio, which also apply to sound harmony and music.

This comment from GerateWohl made me think that yes, while probably not specifically related to the golden ratio, the reason a C major chord sounds pleasing must have something to do with the relationships between the frequencies involved, and how the ear/brain perceives the combined sounds.

And indeed, a quick Google search of “Why does a major chord sound pleasing?” gives this AI overview (the source is Reddit):

“Major chords sound pleasing primarily due to physics and acoustics, specifically because of simple, harmonious frequency ratios (4, 5, 6) between the root, major third, and perfect fifth. These ratios create strong, aligned sound waves that resonate smoothly, minimizing harsh dissonance in the inner ear, which is often interpreted by our brains as a stable, “happy” sound.”

In other words, the frequency of the E (330 Hz) is in a 5:4 relationship with the low C (262 Hz), and the G is in a 6:5 relationship with the E and in a 6:4 (or 3:2) relationship with the C, and the upper C (523 Hz) is in a 2:1 relationship with the low C.

So that settles that aspect of it, then. 🙂