This is a good question.

I have some nerve damage in my left ear, and it has tinnitus which varies during the day. This is a high pitched sound like
static you might hear from a microphone that was not working correctly.

The hum is a global sound in my head, it overpowers the hiss in my right ear and feels like a REAL sound. For me it is like a choral group singing a one note hum. It feels somewhat musical to me. (not like the description from the link I gave).
And sometimes it changes pitch by one note, but not always.
I hear it mostly at our very quiet home up North. We live on
rock...limestone rock...and when it started for me, I thought it was coming up thru the stone. Like a vibration, more than a sound. It also had a distant quality, but was pretty loud.

I've only heard it here a few times, not often.
For me it is not everyday, or constant. But it is WEIRD.