What does "twittering away to itself" mean? Does it mean that the radio is twittering and the sound generated by the radio is outward from it?
White hair endows you with the demeanour of a friendly witch. Our geriatric radio – a wedding-present from my brother – is twittering away to itself. I’m about to knock on the glass, but your laptop screen glows into life: and suddenly here’s our son’s hazy face, bringing you news from across the ocean.
(Excerpted from David Mitchell's novel The Gardener.)