Matt Deveney, 35, musician in Grateful Dead cover bands

Shy and laid back, Matt Deveney was a quiet presence on stage as a keyboardist and occasional vocalist with Grateful Dead cover bands, peering out from beneath the brim of a baseball cap.

"He always played with his eyes closed," said his youngest sister, Grace. "He just enjoyed it so much. He'd be bopping around. He just bounced in his seat. It was kind of cute. The whole band would stop, and he would have a solo, and the band and everyone else would be looking at him."

Despite his unobtrusive personality, people listened to Mr. Deveney, whether they were audience members or customers at his family's monument company in Dorchester. He died Tuesday in his South Boston home of a rare sarcoma of the digestive system. Mr. Deveney was 35 and was diagnosed in January.

"He's the most mellow guy you'll ever meet, ridiculously mellow," said his sister, who lives in New York City. "He was always just the best big brother."

Gerard Matthew Deveney shared his first and last names with his father, but was always known as Matt. He grew up in Cohasset, where he was 7 when his mother signed him up for piano lessons.

"He loved it from when he first started," his sister said. "He stopped taking lessons when he was 15 or 16 and started playing by ear. He played all the time."

Over the years while traveling the country with different Grateful Dead cover bands, Mr. Deveney accumulated about 10 keyboards, each worth thousands of dollars. Most recently he was a member of Playin' Dead, which performed at venues in Massachusetts and elsewhere in New England.

"With everything else in his life, he could take it or leave it; he was always late to work," his sister said. "But with the band, it was like, 'I've got rehearsal.' He never wanted to disappoint his band."

He was just as devoted to his role as the oldest sibling in the family and the only boy.

"He was so funny about his sisters," Grace Deveney said. "He was so proud of us. He always had to introduce us to his bands, a man who was always surrounded by women."

For the past decade, Mr. Deveney ran his family's monument business in Dorchester, which was founded in 1946 by his great-grandfather and grandfather. In a history posted on the Deveney & White Monument Co. website, Mr. Deveney traces his family's roots in the granite industry back to the Quincy quarries in 1898.

"I am proud to be the fourth generation of Deveneys to design these beautifully handcrafted memorials," he wrote.

He was as laid-back as a businessman as he was on stage, and he dressed much the same, which turned out to be a successful approach, his sister said.

"My mom's always trying to get him dressed appropriately, and he was always wearing his T-shirt, jeans, and baseball cap," she said. "But he could sell anything. You could tell he wasn't try ing to swindle anyone. He had such a sweet personality everybody liked him. And he was so kind to everyone who was coming in at a hard time. He was a good listener."

Mr. Deveney's sister Elizabeth had been living in New York City during the terrorist attacks of Sept. 11, 2001, Grace Deveney said, and "it had a profound effect on her." Elizabeth Deveney , who now lives in Boston, made some changes, including traveling to see more of the world.

She and another sister, Sara Norris of Scituate, decided to embark on el Camino de Santiago. The pilgrimage from St. Jean Pied de Port on the French side of the Pyrenees to Santiago, Spain, is known as The Way of St. James.

After they had completed the journey, Grace Deveney and Mr. Deveney were at a bar "and I said: 'Well Matt, I'm going to do the Camino. Do you want to go? We've got to complete the circle with all four of us doing it.' "

At the outset, Mr. Deveney was a bit out of shape, "and I'm chatting beside him, and he said, 'Are you going to talk the whole way?' But in the end he was way faster than I was," she said.

They completed the trek of 500 miles in 30 days. As they walked into Santiago, "he was singing songs," she said. "It was one of his proudest accomplishments. He told every Spanish person when we got there, 'I just walked 500 miles.' "

In January, Mr. Deveney was diagnosed with gastrointestinal stromal tumors. The family pulled together to care for him, along with his fiancee, Keleigh Quinn of Boston.

"He was just amazingly brave through the whole thing," Grace Deveney said. "He knew he wasn't going to get better. The first thing he said was, 'I'm really going to miss you guys.' But he never, ever complained."

About a month ago, the members of his band came to pay a final visit and Mr. Deveney suited up with his ever-present baseball cap to greet them at the door. In the past couple of weeks, he was too ill to get out of bed without assistance.

"One day he put out his hand and I said, 'Do you want to get up?' because he couldn't get up on his own," Grace Deveney said. "And he said, 'No, I just want to say thank you.' "

In addition to his sisters Sara, Elizabeth, and Grace, and his fiancee, Mr. Deveney leaves his parents, Gerard and Margaret of Cohasset.

A memorial service will be held at 4 p.m. today in South Shore Baptist Church in Hingham. Burial will be private.