Heaven observed: head turns when this happens, by the sound of it? (4,5)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

definition: ‘next world’ refers to a life after death sounds like/”by the sound of it”: ‘Neck’s twirled’=”head turns when this happens” is “observed” there to justify the past tense in ‘twirled’?