Casting father and daughter in a drama loosely based on their own relationship creates a fuzzy line between reality and fiction in You Sing Loud, I Sing Louder.

This uneven indie road-trip drama is at times too by-the-numbers but is always captivating thanks to its two stars, who hold the screen throughout. Ewan McGregor plays a landscaper with a pickup truck driving his daughter, played by Clara McGregor, to a destination he doesn’t share with her, or with us, until well into the film. We immediately see the distance between them, though, which is as vast as the wide, empty New Mexico landscape they’re passing, a lonely expanse of desert and scrub. He is clearly nervous with worry, and she is belligerent. Their characters have no names, a device that doesn’t serve any purpose, because these people are very specific. But the slow reveal of information works better than the no-name trick,...