Top-billed speakers took the stage midday, as the DC heat reached its climax, with Lin Manuel Miranda singing a lullaby for separated children — and assembled crowds were totally undeterred as temperatures climbed. You can’t pay to hear Miranda singing on Broadway anymore, after all, but if you showed up Saturday, you heard him.

Miranda was singing “Dear Theodosia,” from his hit musical Hamilton, known for its celebration of America as a nation of immigrants. And he sang with words unaltered — a way, perhaps, of emphasizing its universality — as many in the audience sang along, becoming a near chorus on the refrain, “Someday, someday.”

“Don’t stop. Don’t give up,” he told the audience, as he waved off stage.

Next up, Alicia Keys told sweat-drenched crowds she came less as a star than as the mother of a seven-year-old son. “His name is Egypt and I couldn’t imagine not being able to find him. I couldn’t imagine being separated from him,” she said. “If it can happen to one child it can happen to any child,” she said.

But perhaps the most powerful language came from actress America Ferrera, who said she came, above all, as a human.

“I’m here not only as a brand new mother, as the proud child of Honduran immigrants, and not only as an American who sees it as her duty to be here defending justice. I am here as a human being with a beating heart, who understands compassion and can easily understand what it must feel like to struggle the way families are struggling right now,” she said to cheers from the audience.

“It is easy to imagine and I would hope if it was my family being torn apart,” she added, “then someone would stand up for me and my family. It is that simple. This fight does not belong to one group of people, one color of people, one race of people, one gender — it belongs to all of us,” she said.

Every so often, the crowd erupted in boos or exclamations of, “How dare they!” But overwhelmingly, those in attendance maintained an elevated mood. As Ferrera and Keys read testimony from people affected by Trump’s zero-tolerance immigration policy (names were changed to protect identities), they chanted “Love is love,” or hummed strains from the passing lullaby.

Keys told the story of “Margarita,” a mother who’d been separated from her son “Carlos” since before Christmas. Said the mother in Keys’ testimony: “First they tell you in a few weeks you will have your child, then in a month, then in another month, but they never fulfill their promise.”

Testimony read by Ferrera focused on am Oakland-based grandfather hoping to be reunited with his granddaughter Theresa — but Ferrera also encouraged people to imagine all the stories that go unread.

“What makes humans remarkable is our capacity to imagine. We have an imagination let’s use it,” she said.

And so, they have. With signs that read, “Don’t shoot — I’m white,” and dressed in costumes from the Handmaid’s Tale, toting their toddlers, holding hands, cursing the heat and playing tibetan singing bowls, the crowds are beginning their march down Pennsylvania Avenue, headed toward the Capitol, their final destination.