I will be in Paris 9/2-9/18 and would love to see a concert or ballet at the Palais Garnier. When I was there once we walked about and did a self guided tour. They had a treasure hunt going on with dancers/actors in costume. It was magnificent. Any suggestions as to what to see and how and when to book tickets? I am not sure how to access this info online; feeling a bit overwhelmed by it all. Thank you in advance.
If you look at https://www.operadeparis.fr/en/programme-and-tickets you will see the events at the opera houses and the philharmonic.
Looking at the schedule during your timeframe, there is one performance that has available tickets, which start at 165€ each. All other events are in different concert halls and the Bastille opera.