In a bucolic village high in the Tibetan mountains, easygoing mastiff pup Bodi (voiced by Luke Wilson) is supposed to inherit the mantle of town guardian from his broad-shouldered father (J.K. Simmons). But his true calling is music, and he will not be deterred -- not even when his father confiscates every musical instrument in town after a devastating wolf invasion decimates the local sheep population. One day, a radio drops from a cargo plane flying overhead, and Bodi ends up enthralled by the rock music of Angus Scattergood (Eddie Izzard), a languorous white cat made from equal parts David Bowie and Keith Richards. Sensing defeat, his dad buys him a bus ticket to the big city, where he will be free to seek his fortune. But once the nattily dressed wolf syndicate realizes he's left the kennel, they drop their martinis to reel in their choice prey.
So let's get this straight: A furry misfit living in a grim locale discovers a creative calling that is expressed visually as an ecstatic, synesthetic experience (like Ratatouille). He travels to an anthropomorphically populated metropolis (like Zootopia), where he joins a community of aspiring animal music makers (like Sing). Along the way, he gets on the nerves of a would-be mentor who gradually comes around to him (like Babe), and he eventually finds an alternate, purer, more joyous use for his power (like Monsters, Inc.). Have we missed anything? Oh, yes, it's all narrated by a wise and bemused water buffalo voiced by Sam Elliott, exactly as he lent his seismic rumble of a baritone to The Big Lebowski.
You wouldn't know it from looking at most of Hollywood's output, but there's no mandate that children's movies must operate around the theme of "be yourself and follow your dreams." Many great children's movies are about other things, such as facing your own insecurities and resolving interpersonal conflicts (Toy Story); realizing one's overlooked potential (The Lego Movie); coping with mortality (Charlotte's Web); celebrating the many faces of love (Frozen); or defining a personal moral compass (The Iron Giant). Even if Bodi's gee-whiz enthusiasm is sort of charming (although his knit cap and well-weathered instrument bring to mind that guy around campus who's always playing hacky sack) and there's nothing offensive or repellent about this admittedly acceptable film for kids, there's also nothing enthralling in it for anyone over the age of ten. Rock Dog wants to be the Jeff Buckley of kiddie musicals, but it's really Hootie and the Blowfish -- perfectly fine, until the day you know enough to know better.