There’s a sense of unstructured play about “Different Drummers,” a kind of ambling from one whimsical activity to the next without much regard for following rules of tidy, traditional storytelling.

In its roaming way, this independent feature set in 1960s Spokane is like its subject: the backyard adventures of two boys for whom nature and imagination have boundless possibilities.

Written and directed by Don Caron and Lyle Hatcher, and based on true events, “Different Drummers” is about the friendship between grade-school kids David (Ethan Reed McKay) — who uses a wheelchair and is losing ground to muscular dystrophy — and Lyle (Brayden Tucker), whose impulsive energy finds relief in a desire to run.

The physical and emotional contrast between the characters — gloomy, tentative David and the Huck Finn-like Lyle — is the stuff of classic children’s literature. It’s also perfect ground for exploring an unlikely bond as the boys gather spiders for a science project, face airgun-toting bullies and plan a fundraising stunt.

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One of the film’s strongest achievements is capturing an era both different and not-so-different from our own. On one hand, there’s no zero-tolerance brouhaha when Lyle reveals his old Cub Scout pocketknife at school. On the other, Lyle is overmedicated for his attention-deficit disorder.

There are patches of dialogue in “Drummers” that suggest the film might shape up as a Christian drama. That would have been fine, but Caron and Hatcher finally veer from that and appeal to a mainstream audience. Deservedly so.

Tom Keogh: