Weird SS chain rattle?

The chain on my commuting fixie has a weird rattle – higher pitched than you’d expect, it sounds exactly like a loose spoke. And it’s coming from the chain – flicking the chain directly causes this high-pitched rattle.

I’ve taken a quick look and can’t work out what’s up with it – there are no obviously half-broken links. Should I be worried?!
Chain is a KMC 3/32″, fwiw.
Cheers

Twisted tooth on the front or rear?

Cog tightened onto the freewheel tight enough?

Thanks, will check those. Think the sprocket’s on tight enough – no obvious slipping when slowing down.
Cheers!

Oldish chain? Mine makes that kind of noise when worn and dry. I think it is the bushings rattling on the pins.

Try oiling it.

Loose chainring bolts?

any change in chain tension?
shouldn’t be loose chain sprocket but might be ‘off’