Friends draped arms across one another’s shoulders and swayed as they listened to Forrest Allen sing. Some joined in softly, not wanting to drown him out. Some blinked back tears.

They never expected him to survive the accident. They knew the effort it took that afternoon for Forrest to sing each note — just audible, even with a microphone — as his music therapist played keyboard next to him. His brother steadied Forrest with a hand to his back; with so much of his skull missing, a fall could be deadly.

Forrest stopped in the middle of “Lean on Me.” He grinned at the graduation-party guests gathered on the lawn of his family’s home in Virginia horse country. “You guys aren’t singing!” he teased. They laughed, and raised their voices along with his.

Forrest is 21. He was supposed to graduate from high school three years ago. Then he caught an edge snowboarding and fell, hard. For two years Forrest couldn’t say a word.

When he was finally able to type, he tapped out a message to his childhood music teacher: “Mr. Sweitzer, please help me get my voice back.”

Music therapist Tom Sweitzer and Forrest Stone Allen rehearse their songs at A Place to Be in Middleburg. (Nikki Kahn/The Washington Post)

Life changes in an instant for millions of people each year who, like Forrest, suffer traumatic brain injuries. Such injuries — whether from an IED in Afghanistan, a tackle on the football field, a fall off a ladder or a car accident — kill and disable more young people in the United States than anything else. More than 5 million people are trying to recover from them, at a staggering emotional and financial cost.

For Forrest, help came from places both expected — family, friends, teams of medical professionals — and unexpected. Tom Sweitzer used rhythm and melody to motivate him through the endless repetitions of neural recovery, coaxing out breathing and movement and laughter and, finally, Forrest’s own words. Cheering him on was a team of supporters — all of Middleburg, it seemed: old classmates, nurses and teachers, and thousands of strangers who followed online updates.

Those who came to the party in June had been waiting for this moment: graduation, celebration, a chance to hear Forrest sing. It was something to hold onto, a moment to savor before the next hit.

This month, Forrest will undergo the first of a groundbreaking series of surgeries to try, once again, to close up his skull.

It could save his life. It could wipe out everything he has so painfully earned back.

Ponies and dolphins

Forrest grew up riding ponies on his family’s farm in The Plains, Va., just outside Middleburg, and climbing in tree forts with his older brother, Austin. He spent summers scuba diving wherever his mom’s career as a marine mammal veterinarian took them, swimming with dolphins.

He was fun-loving, polite, silly, charismatic — and could talk his way out of anything, said Sweitzer, who has known him since kindergarten.

He spoke up for underdogs. There were tight cliques at the Hill School, but Forrest was always the one to bring everyone together, with sleepovers, parties and paintball fights. “He just had a lot of empathy for everyone,” said former classmate David Marshall.

He wanted to be a veterinarian, like his parents, and had been accepted into the president’s leadership program at Christopher Newport University in Newport News.

Soon after his 18th birthday and a family trip to Aspen, Colo., where he and Austin rode some of the toughest slopes, Forrest went snowboarding at a little ski area in Virginia.

This time, he didn’t wear his helmet.

He fell so hard that he shattered a wooden fence.

Doctors in Charlottesville, where Forrest was airlifted, told his family to prepare for the likelihood that he would never emerge from the coma, recalled his mother, Rae Stone. Surgeons cut out the front third of his skull to relieve pressure on his swelling brain.

But after 10 days, Forrest opened his eyes and squeezed Stone’s hand.

As Forrest began to recover, there were small signs that his personality, though silenced, wasn’t completely lost. On a medevac flight to a rehab hospital, a nurse handed him a stress ball. Forrest made his family laugh by playfully dropping the ball back in the nurse’s pocket.

After hours of a drill where a physical therapist asked him to hold up two of his fingers, he tired of doing it. So when she said, again, “Show me two fingers, Forrest,” he pointed at her fingers, and smiled.

But after doctors closed up his skull with a prosthetic plate, he went back into a coma. Racked with seizures and hallucinations, unable to breathe on his own, his 6-foot-3 frame dropped to 118 pounds.

Finding his voice

His condition was so precarious that Team 44 — as his loved ones called themselves, after his childhood nickname and lacrosse jersey number — didn’t look ahead very far. They focused on 12-hour plans. His family stayed with him in shifts around the clock, reading cards aloud and watching silly movies, despite his silence. Friends told funny stories over Skype.

Stone asked Sweitzer to come, hoping a familiar voice might trigger some response. Sweitzer played guitar and felt like a failure; Forrest seemed catatonic, he said. But Stone saw Forrest’s pinkie move to the music.

Over time, there were other glimpses of Forrest’s personality — a reassuring thumbs-up, a flash of his dimpled smile. When he came home from the hospital shortly before Christmas 2011, he required 24-hour nursing care and was still on oxygen and a feeding tube. But Sweitzer was able to visit more regularly.

They spent months working on breathing, or hitting a drum. Sweitzer used music, often the silliest of songs from cartoons, or pirate fights, to motivate his patient.

“I’m worried about the same thing the physical therapist is worried about,” Sweitzer said. “How many times can you cross the midline of your body to hit a drum?”

Forrest had both physical and cognitive gaps, typical of brain injuries. After two years of intensive therapy, he could understand a 12th-grade government class, but struggled with short-term memory. He was learning to use a keyboard, but was unable to speak and was unsteady on his feet.

As the 2012-2013 school year began, Forrest’s parents met with specialists at Fauquier County Public Schools, who laid out an education plan for a non-verbal person. Stone told them no — her son was going to talk again. They thought she was crazy.

In October, after months of effort, he was able to blow into a whistle enough to emit a tiny noise.

Later that fall, Forrest typed the message to Sweitzer asking for his voice back. After leaving the house, the music therapist broke down. “I knew Forrest was trapped in there,” he said.

The signs kept coming: same warmth, same playfulness. In his first typed message to a longtime aide, Forrest wrote, “You are a — ”

The aide waited breathlessly. What was it he wanted to say?

“ — nincompoop,” Forrest typed. They both cracked up.

Sweitzer kept trying to get Forrest to say words, to greet him when he arrived. In December 2012, he saw Forrest’s mouth forming, then heard the slightest sound, half an exhale, half a hum: “Good morning.”

It was afternoon but, Sweitzer said, they all laughed, elated. It was morning somewhere.

For the many months his son was silent, Kent Allen said, he kept thinking, “I’ll give anything in the world if you’ll just say yes or no.”

Once the words started to return, “you want more,” Allen said. “You want him to live a normal life.”

A starring role

“Eeeeeee,” Forrest said on a recent afternoon, trying to hold a note as long as he could at Sweitzer’s music therapy center in Middleburg. Sweitzer held up his phone to time the seconds.

“That was 21,” Sweitzer said. “Can you make it to 30?”

Forrest pounded out an ominous little crescendo on the piano keys with one hand. His mouth twitched into his ready smile. His “bucket,” a big white helmet signed by friends, and his service dog, Toliver, were at his side. He had tied a bandana around his head. It dropped starkly in front where his skull is missing.

“Eeeeeeeeeeeee,” he said.

For the past six months — since Forrest got out of the hospital after a third failed attempt to close his skull — he and Sweitzer have been working on a musical about Forrest’s life. It is by turns serious (information about brain injuries), goofy (“Dolphins, flying through the sky. Dolphins, eating pies.”) and heartfelt.

In the musical, titled “44,” Forrest thanks his brother for putting his life on hold for years to be there for him. He sings about the trapped feeling of wanting so badly to talk. He says he sure wishes he had worn a helmet that day.

His voice is weaker than it was last year, before the last, terrifying setback. But he can still talk trash during a ping-pong match, or sing along when friends play guitar.

Of all the many types of therapies he has to do, including speech therapy, music feels different, Forrest said. Sweitzer “makes it fun. I like going to it.”

At the beginning of summer, Forrest and several students read “44” to a packed auditorium at the Hill School. They plan to perform the play in October, but wanted to stage it early, just in case.

After three failed attempts, surgeons are trying a more extreme way to reconstruct Forrest’s skull and protect his brain. The protocol was designed by U.S. doctors serving in Iraq and Afghanistan to help brain-injured soldiers.

A team of doctors at Johns Hopkins will work to create a layer of living tissue on Forrest’s head by moving a flap of muscle there during an initial 10-hour surgery later this month. Eventually they plan to remove part of the healthy bone from the back of his skull, split it, and implant a piece on the front, behind his forehead.

“It kind of makes me sick to think about it,” Stone said. The risk. The hospital time. She’s most afraid of a return to silence.

Forrest says he’s ready. He told Sweitzer he would either wake up happy, “or, pfff.” He made a funny noise, like air coming out of a balloon.

When Kettle Run High School’s class of 2014 marched into the football stadium on graduation day, Forrest walked with it, mortarboard shimmied onto his helmet. He grinned and gave a thumbs-up when he saw Team 44 waving a giant photo of his head.

After the ceremony, his mom told him: You did it! You’re done!

No, Forrest said. I’m not done.

For a moment she thought he was confused. Her heart clenched. “ ‘Have we got a bleed?” she wondered. “Is there a setback situation here?’ ”

It was neither. Forrest wasn’t confused. He just had something to say. “There’s still college.”