I believe there are ways of keeping chunks loaded (multiple players etc). I was under the impression that circuits still operate, but you can't *see* any outputs, such as lamps or pistons extending for example unless that chunk is loaded.
So if you push a button whilst in a chunk that powers a load of repeaters that go out into the distance (into unloaded chunks), turn around, come back and play a note block next to where you're standing, it should still work.