If you're like me, then while playing the game you feel really 'stressed' (stress isn't a good word to describe the feeling, but it's a pretty unpleasant feeling in your chest) and find it hard to continue down that long dark hallway. Singing helps, especially if it's something like the following:
http://www.youtube.com/watch?v=kvpyz6MUa1w
http://www.youtube.com/watch?feature=pla...1D8#t=446s
http://www.youtube.com/watch?v=w_qGh9kJaOE
http://www.youtube.com/watch?v=APD75lWDMMQ
http://www.youtube.com/watch?v=lS1Y-Cgn1GM
There isn't anything wrong with playing music in the background while playing Amnesia. I did it at the worst parts of the game for me.
It really is hard to not be scared by the Prison. That part of the game took me the longest to get past because I was so scared by it. You'll feel like a better person once you complete it, though.