DENILIQUIN, Australia — It’s been called the most debauched outdoor party in Australia: a wild, rollicking weekend where rural masculinity is on display and beer and banter flow endlessly.

But for the Thompsons, the event carries more weight and meaning. They first went to the party, the Deni Ute Muster, three years ago, not long after losing their son, Bryan, to suicide.

Bryan’s mother, Lyn Thompson, 54, said she just knew it was his kind of festival. She pulled some faded pictures from her wallet, showing a son who had been eager to grow up, she said — a tall, 24-year-old bricklayer raising three children in small-town Australia with a heavy burden of responsibility.

“When we’re here, he’s with us,” she said. “When we’re anywhere he’s with us. But especially here.”

“Here” is Deniliquin, a small farming town in rural New South Wales, where thousands of people from around Australia come for a weekend outdoor festival built around the “ute,” Australia’s beloved utility truck. Conceived of 20 years ago as a way of giving the local economy a lift, the festival, or muster, has become a juggernaut of rural identity: Almost 20,000 people attended last weekend’s muster, which featured Carrie Underwood, the American country music star.