Dermot Mulroney is not only a talented actor but a gifted cellist. In fact, this is actually him playing in this scene! Dermot has played on numerous film scores including JURASSIC WORLD and INSIDE OUT. In 2009 he attended the Acadamy Awards as an orchestra member.
Not surprisingly, finding a day when Lang Lang, Emanuel Ax, Joshua Bell, and Alan Gilbert--all classical music elite--were all in New York and available was like a Tetris puzzle. The party scene had to be shot almost a month after the rest of the episode. It was one of the best days of Jason's life. He said "Seeing Lang Lang and Joshua Bell hanging out in the corner of a bar in Brooklyn" was why he was doing the show, for moments like that. He added "Everyone was so cool and totally happy to embrace being out of their element." Jason said that after working with Emanuel Ax, he hopes Emanuel can adopt him because "he's the greatest and made me laugh. Every single take was just funnier and funnier and better and better than the one before."
After the table read, Gael came to the writers to express his concern that the scene wasn't pushing the characters far enough--he thought the characters shouldn't just be talking about life or music, but everything. Jason and Alex Timbers played with writing it out but decided to try something the show hadn't done before and let the actors improvise. They made a list of prompts, then Jason and Roman held up cue cards with prompts like "DEATH" for the actors to go anywhere they wanted, all in one forty-five minute take.
This particular day the earpieces malfunctioned an each person heard things at slightly different times. Gael conducted and the orchestra followed his cues, however, due to the technical glitch the players were out of sync. The error was quickly solved but it proved to be a significant insight into Gael's prowess. Dermot noted to director Jason Schwartzman that the orchestra followed along with Gael's movements perfectly, rather than just following the music..he had truly become their maestro.
The Ping Pong scene originally featured the musicians bowling. Lang Lang suggested Ping Pong because he actually does play to unwind and said realistically the musicians wouldn't go bowling because of the risk of injury to their hands. Like the tent scene, Lang Lang and Joshua Bell played for ten minutes while the cameras rolled.