NORTH ADAMS, Mass. — “This is my son Spencer,” Jeff Tweedy said onstage at the Solid Sound Festival on Sunday night, presenting his new band, Tweedy, by introducing its 19-year-old drummer. A moment later he caught himself, observing that this crowd probably didn’t need to be briefed. But he went on, “just in case somebody wandered in,” he said, “and didn’t realize it was a cult gathering.”

Solid Sound, which drew about 8,000 people here from Friday through Sunday at the Massachusetts Museum of Contemporary Art, is built around — and largely by, and on some level for — Mr. Tweedy’s long-running primary band, Wilco.

Wilco fandom isn’t a prerequisite for enjoying this festival, but it sets the conditions for a specific vision of utopia: a convergence of grown-up indie tastes, with subsidiary interest in American roots music, multimedia projects, comedy, jazz and performance art. Also guitars and kids, both in abundance.

Smoothly run by Wilco and its management company with the concert promoter Alex Crothers, Solid Sound is determinedly upbeat, inclusive and family-friendly. “The only real desire was to make a festival that we wouldn’t be miserable at,” is how Mr. Tweedy puts it in “Every Other Summer,” a documentary produced by Trixie Films and just released on Vimeo. (That title refers to an on-again, off-again schedule that began after 2011, making this year’s edition the festival’s fourth.)