Some movies grab the audience; strap it down, force it to gorge, like a multiplex theatre full of foie gras geese. The oeuvre of Mike Mills is not like that. Watching his films – gently unobtrusive when it comes to plot but rich with emotional texture – can be like looking at a painting in a gallery. You can, if you choose, walk away taking virtually nothing from the experience. Or you can delve deep and discover whole worlds within.

His latest, C’mon C’mon, is perhaps his most stripped-back to date. Centred on an impromptu road trip across America that explores the bond between an uncle, radio journalist Johnny (Joaquin Phoenix), and his nephew Jesse (Woody Norman), the film is shot in black and white. It’s an aesthetic decision that brings a muted melancholy to the exuberant, palm-studded skyline of California, and tones down the carnivalesque drama of New Orleans, the better to draw the audience into the quiet heart of the film.

This is a movie about listening – really listening – to what other people have to say. Johnny’s work involves interviewing kids, tapping into their hopes and fears for the future. Jesse, an eccentric, endearingly odd nine-year-old, refuses to be recorded but immerses himself in the sounds around him. And through a series of late-night phone calls, Johnny and Viv (Gaby Hoffmann), Jesse’s mother, reopen the lines of communication that were felled after the death of their mother.

Appropriately, sound and music are key; the soundtrack is uninhibited and eclectic, veering from opera to Lee Scratch Perry to Lou Reed’s pre-Velvets novelty track The Ostrich. But the film’s main assets are three extraordinary performances: Phoenix, rumpled and emotionally untucked as Johnny; Hoffman, loving and hurting fiercely as Viv; and Woody Norman, delivering one of the most remarkable performances, by a child or otherwise, of the year.