Appropriate music for civilization's downfall is going to depend pretty enormously on how said downfall comes about, no? The music for a zombie apocalypse would be horribly out of place in a robot uprising, and the tunes that evokes would mesh horribly with being nuked into oblivion by Shaka.
I should think, though, that any likely scenario is likely to lead to being far more carefree- after all, your likely responsibilities will be limited to sustenance, shelter, rebuilding society, and possibly repopulating the earth; no more dress codes or parking tickets, no more keeping up with the Joneses or worrying about offending someone by serving Ding dongs with white wine instead of red. Granted, there are dangers in recklessly over-betting how many nosalises it would take to kill a bloodsucker, but that's hardly unavoidable.
And what would I miss? Reliable electricity. Without that, I can't run the machinery that keeps my brain from killing itself while I sleep.