Urgent please: If one is modern Orthodox without any particular affiliation to either Sephardi or Ashkenazi, can one listen to instrumental background music while working on a computer, shave and watch TV at home? Is going to a movie theater permitted with a friend on a rare visit from Israel during this time?
The custom is not to listen to music in the three weeks, as a sign of mourning over the Bais Hamikdash.
Regarding going to the movies to entertain a friend on a rare visit, although many people go to movies, watching movies very often is problematic. One of the reasons is because the actresses are usually dressed scantily and provocatively, and because it promotes promiscuous behavior. Maybe try doing something else with your friend.