I don't listen to music when I write, but I do turn on appropriate music when I read portions of my manuscripts back to myself - kind of like adding a soundtrack to help shape mood. ↗
In Brentwood we had a big safe-deposit box to put manuscripts in if we left town during fire season. It was such a big box that we never bothered to clean it out. ↗
A typical agent in New York gets 400 query letters a month. Of those, they might ask to read 3-4 manuscripts, and of those, they might ask to represent 1. ↗