Director Sidney Lumet writes in his book "Making Movies" about an argument between River Phoenix and writer Naomi Foner. A scene in the movie concerns the character played by Phoenix being interrupted while practicing a classical piano solo. In the script, when he is caught, he breaks into a jazz riff to cover his "embarrassment" at being caught doing something serious. Phoenix fought hard against this, feeling that his character would never be embarrassed about working at the piano. Lumet was so impressed by the point Phoenix made, he shot the scene the way Phoenix wanted it.
Although River Phoenix learned all the hand motions to the piano pieces his character performs in the movie, the audio was dubbed by a professional pianist.
During a 2016 Q and A session at Austin's South by Southwest Film Festival, Jake Gyllenhaal (whose mother, Naomi Foner, wrote this movie's screenplay) recalled that he was allowed to sit in on two weeks of rehearsals before filming started. The rehearsals made a profound impression on Gyllenhaal, who was six years old at the time; he recounted what he could remember about Sidney Lumet's process: "I do remember the process of exploration, kind of that feeling that there were no rules in that space. I remember River Phoenix asking questions about things that he wasn't sure about, that he didn't really know, and then it would resolve something in the screenplay where, you know, it 'read well,' but then it wouldn't be playable, and he would ask the question and all of a sudden it would become playable and emotional. You could see the actor's instinct kind of open up in their scene. I remember also Sidney Lumet finishing the day really early, because he got what he wanted in six hours. I remember all these really weird things and had no idea who I was around. It's not until now that I realize what an extraordinary privilege and amazing time it was to be amongst that." Gyllenhaal also recalled having a crush on Martha Plimpton at the time.
River Phoenix (Danny Pope) was dating Martha Plimpton (Lorna Phillips) during filming. They had been dating since the production of Mosquito Coast (1986) two years earlier.