Wow this does look like it was a fun time. I have no idea what that octopus hose thing in picture 4 (with all the what look like champagne bottles on the floor) is though, can someone explain it to me? Sorry for being a plebe.
The party took place at the Phonograph museum.
These actually are earphones from the beginning of the 20th century, they're plugged into a phonograph. Some people would buy a phonograph and go from fair to fair. It was used as a kind of amusement machine: people had to pay to listen to the music burnt into the roll. Several persons could listen to the music at the same time, that's why there are several earphones.
The guy you see playing the piano is the best french caravan mode player. He played some PCE tunes on the piano (Final Soldier, Jackie Chan, Aldynes, etc.). How classy is that?