As I said, it was an interesting exercise, and the sound of the distortion is quite unique - I may even turn this into a kind of “distortion effect”
Ah yes, you noticed that too. Weird isn’t it.
You mean like “high frequency selective enhancement”?
A technique that was sometimes used in the old analogue days (particularly for drums) was to slightly overload the recording tape (“tape saturation”). This causes a kind of “soft distortion” (as well as “dynamics compression”).
Most forms of distortion add upper harmonics to the sound - the difficulty is in finding a distortion that creates “pleasant” upper harmonics.