I'm pretty sure that sounds of different kinds are not too upsetting for chickens. My first flock was when I lived in town on a corner lot with lots of traffic.
On my country property the chickens have been unfazed by military helicopters overhead, the lawnmower, parties we've held, the crew...
No, I haven't tried that.
It probably won't hurt if it doesn't annoy the neighbors (I have a GREAT hatred of hearing someone else's music when I'm in my own yard and always wear earbuds or headphones so that my music doesn't bother anyone else). I don't know if anyone ever studied music with...
I don't have any links handy, but I believe that people have tried 24 hour light to see if that improves laying and found that it had a negative effect on the chicken's health over time.
That said, many urban/suburban chickens live in areas that are never truly dark because of streetlights...