Harry Gartzman had a stroke in June at his grandson's wedding. The ceremony had ended, and he walked out with a big smile. Suddenly, he couldn't move on his right side, or talk.

"If you were to stand on his right and speak to him," said his granddaughter, Mia Sclafani, an emergency-room doctor, "he wouldn't even know you were there."

A stroke of this magnitude at age 92, she said, "is usually incompatible with life."

Harry's family was worried, of course. So were friends at the Philadelphian, a condominium near the Art Museum where he'd lived for 15 years. Harry was indispensable as piano player at sing-alongs and holiday parties - most notably, Christmas.

"There was chronic depression in this group," said Joe Moloznik, 85, a singer in the holiday ensemble. "It carried over from the group to others in this building."

Harry had begged for piano lessons at age 8. He played a saloon, Augie's, in Camden, by 14. He paid his University of Pennsylvania tuition, $300 a year in 1937, by playing parties. After three years at war, he played right through the Philadelphia College of Osteopathic Medicine.

He did well, becoming a family physician in Camden and Pennsauken, president of his synagogue, president of the Camden County Medical Society. And the music never stopped.

In recent years, Harry played love songs on Valentine's Day, Irish ballads on St. Patrick's Day, Sousa marches on Independence Day. But his first love had always been Cole Porter, George Gershwin, and the Great American Songbook.

After the stroke, Harry was rushed to Thomas Jefferson University Hospital. Even in the first hours, as he regained a bit of function, "you could see him trying to test himself, making fists," said his granddaughter. "The left hand responded, and the right didn't. He'd keep doing this and slowly got a little better. You could see his fingers moving as if he were going through the chords on the piano. . . . He was practicing on the air piano, seeing what he could do."

After four days, he was moved to Magee Rehab. On a "tour," Harry saw an old piano, a Lester. Once made in Philadelphia, Lester pianos are even older than Harry, and this one was horribly out of tune. But a therapist asked if Harry would like a keyboard, and one was brought to his room.

"You can't imagine the frustration when I first sat down and tried to play," Harry recalled. "I knew where my fingers should be, but they didn't know."

Being a family physician, Harry understood exactly what had happened to him, the aphasia, the paresis, to use medical terms. Seeing how limited he was at the keyboard, he wondered - would he ever be himself again?

Harry had been an amazingly vital man. Before the stroke, he was taking history at Temple's Center City campus, going to jazz on Friday evenings at the Art Museum. He was a regular at Citizens Bank Park, wearing his baseball cap that reads "Phillies" in Hebrew.

His granddaughter, who had her own place at the Philadelphian while in medical school, often joked to him that "you have a better social life than I do."

They graduated from the College of Osteopathic Medicine 55 years apart, and turned heads just weeks before the stroke, dancing together at the annual reunion.

"Don't tell them you're my granddaughter," Harry pleaded.

Harry was married 47 years. When his wife died in 1996, he remarried the mother of his daughter's best friend. When she died in 2003, he resumed dating.

"I've met a couple of [his] lady friends," said Mia. "He still has this girlfriend from 18 that calls him. Her name is Rosalie. She was sending cards and flowers in the hospital."

Harry had two children - a daughter, Mia's mother, and a son who went to medical school and joined Harry in the family practice. But only months later, at age 30, the son died in a head-on collision, leaving a daughter and infant son.

Naturally, Harry became exceptionally close with that grandson, Steve Gartzman, at whose wedding Harry suffered the stroke. Steve, 27, who now lives in Collingswood, also loves music and often jammed with his grandfather.

"He's on a completely different level than me," said Steve. "I play the guitar, but he's a musician. When we would play together, we would try to find common ground. He was mostly old-school jazz and, as much as I liked that, I liked classic rock. We would come together mostly on the 12-bar blues. I'd try to sneak in a Phish song every now and then."

Steve was distraught when his grandfather collapsed, but Mia and others told him not to let it ruin his wedding day. Harry would never want that. The next day, before going on the honeymoon, Steve stopped in at Jefferson.

"He was in pretty bad shape," Steve recalled. "He couldn't talk to us. He listened, and it looked like he might have something to say, but the words wouldn't come out."

Just before the stroke, Steve had helped Harry renew his medical license online. "He still makes house calls," said Steve. "He has one patient, a longtime friend, and he'll still go to his house when he's sick or needs a prescription."

As June rolled into July, Harry kept sitting down at that keyboard.

What was so upsetting at first - his inability to play - became a source of hope and motivation. Every day he could detect the slightest bit of motor improvement, of muscle memory returning, of fingers beginning to find the right keys. He played for hours every day.

"The fact that I was able to gradually, objectively, notice, observe improvement - that was priceless," Harry recalled. "I began to realize, 'God, I'm going to be OK.' Sitting at the keyboard and playing became an objective measurement of my progress and prognosis."

Mia, 31, who works at St. Joseph Medical Center in Reading, came to see her grandfather virtually every day at Magee. She brought him a 20-disc anthology of Benny Goodman so he could listen to great music when he wasn't playing.

"Music is therapeutic on multiple levels," Mia said. "Relaxing, good for the mind, good for the soul. But particularly with a stroke, it's good for your motor skills, good for memory, exercise for the brain. Stroke affects the brain, so doing music was a huge part in his recovery."

Six weeks after his stroke, Harry was home and continued to improve, to recover, playing his own baby grand piano.

By October, he felt well enough to do a Gershwin program in his apartment, and then a Sinatra sing-along in November.

A few weeks ago, he began rehearsals in his apartment for the big Christmas concert.

A dozen singers came the other evening. They left walkers by the piano, hung canes on their chairs. One woman put her medication bottle on the armrest of the sofa.

"Ain't no one to replace Harry," said Elissa Sklaroff, the group leader.

"He's it," added singer Mona Doyle. "He's the man."

"Musical therapy lifted Harry up out of the abyss," said Jim Rooney, another singer. "And it gave hope to the people who listen to him."

The ensemble ran through 26 classic carols. After a version of "Hark the Herald Angels Sing," Sklaroff told the group, "I think [the key of] C is too high. Let's try G."

She turned to Harry.

"Harry, G."

Harry, who plays every song by heart, concentrated for a few seconds, transposing the notes in his mind, and began playing again in the key of G.

He did this all night.

At rest, his hands look spotted and wrinkled and thick, old man hands. But in motion, the fingers go where they've always gone, and melodies flow.

On Wednesday evening, surrounded by friends and family, Harry, now 93, is scheduled to be back where he belongs, in the lobby of the Philadelphian, playing the Christmas concert. And for many who will attend, that alone will be cause for celebration.