The phrase "frequent refrain" refers to a phrase or line that is often repeated in a song, poem, or speech. It acts like a chorus or a key message that is repeated multiple times throughout the piece. Full definition
To fret about the future of cinema is fairly common nowadays, almost as frequent a refrain as saying that film criticism is dying. (pixartimes.com)
The frequent refrain that open source is a pure meritocracy must be re-examined.» (inc.com)
When The Broad contemporary art museum opens its doors this fall in Los Angeles, it will join the ranks of America's big free museums, reviving a frequent refrain: Why aren't they all free? (fortune.com)