This phrase came up in another thread.
"Folk getting together with like-minded folk to sing a few songs, including the popular songs of the day and maybe 'old songs' - some of which were the popular music of another day."

'Old songs' is an expression almost as fluid in its meaning as 'folk.'
To one who rarely sings songs that are in copyright, 'old' starts (or rather ends,) about the beginning of Victoria's reign. That may be extreme. Chappell's "Popular Music of the Olden Time" goes up to about eighty years before he published it. Plenty of people in folk clubs would side with Bishop Percy, whose "Reliques of Ancient English Poetry" included songs not more than forty years old.
Does 'old' mean 'of our grandparents' time' or 'of our parents' time' or simply 'of our youth?'