It's common for directors and actors who work well together to do so again. J.K. Simmons won an Oscar the last time he worked with Damian Chazelle so not only was the actor asked to play a role in La La Land, he got his choice. J.K. Simmons says that, while his options on the film were limited, he did have two different roles to choose from.
During the Whiplash shoot, he sent me the script and said, 'There's really not much of a part for you. I'd love for you to do one of these two little parts. Let me know which one.' I picked the guy who hates jazz [over playing Emma's father].
Between the two, it appears Simmons picked the right role. While it's a small part that only really has one scene, he gets to share a fantastic dialogue exchange with Ryan Gosling. The role of Emma Stone's father is an even smaller part and, while the character may have had lines at one point, in the final cut of the script the character is seen but not heard.
We're sure J.K. Simmons would have been offered a larger part, but the fact is that there simply wasn't one in the movie for him to play. The movie is almost entirely Emma Stone and Ryan Gosling. The third-billed actor in the film is John Legend, who doesn't show up until midway through the movie and only has a couple of significant scenes himself. Everybody else is a bit player except for the leads.
The early scenes between Ryan Gosling and J.K. Simmonds are fantastic, though. Simmons plays a restaurant owner who has begrudgingly re-hired Ryan Gosling's Sebastian to play the piano for the patrons eating dinner. Sebastian, who loves classic jazz, has a tendency to play music that the owner doesn't want to hear which leads to a tension between the two. Simmons tells The Hollywood Reporter that the two ad-libbed the scene quite extensively, so it sounds like there will be some great DVD extras of the two going back and forth.
While the actress who plays the mother of Emma Stone's character Mia made the credit list, the actor who played her father isn't listed on IMDB. We're sure that he would have, had a former Oscar winner played the role. La La Land is in theaters now and is being released in IMAX theaters for a limited run this weekend.