I am not sure if both the words
“sing of the glories of the past”
and
“sing of the glories in the past”
mean almost the same meaning and natural.


Could you please tell me?

See a translation

I think they mean about the same thing.

The first one, "of the past" makes it sound a little more poetic, I think because of other phrases like "the kings of old" or "the heroes of old" or "the tales of days gone by" or "of times past" or "of the ages" etc.

The second one, "in the past" almost sounds more melancholy, like it is talking about things that exist only in the past, they're over, lost and gone. Good times that we no longer have. That sort of thing.

But the nuance is minimal. I'd only use it in writing to give a subtle tone shift, so "glories of the past" if the tone is about admiring them or if it is poetic about legends and heroes, etc, and "glories in the past" if there is more longing, bittersweet, loss, currently out of reach, or if it's about someone's own former glory who is now too old and has only memories of what used to be grand, etc. So it is a very subtle nuance that might not always matter. It is mostly flavor.