AS THE Quaker City String Band rehearsed the wooden soldier march of its latest routine on a chilly December evening, Jim Fox Jr. blended right into the horde of saxophonists playing through "Teddy Bears' Picnic" and "When Johnny Comes Marching Home." But despite being one alto among many, Fox is responsible for an outsized portion of the cacophony being raised on the second floor of the venerable Mummers band's South Philly clubhouse.

Probably half of the Quaker City saxophonists wouldn't be there on New Year's Day if it weren't for Fox. That's literally the case for two of them, Fox's college-age sons, who are carrying on the family tradition. (Jim Fox Sr., 88, who introduces himself as "the real Jim Fox," watched the rehearsal from the back of the room.) For the rest of them, Fox Jr.'s 30 years of teaching have started countless young musicians on the path to that parade route and beyond.

"He was a mentor, a role model and a father figure all wrapped into one," said tenor saxophonist Michael Brown, who followed Fox's lead not only into the Quaker City band but also into a side career playing weddings on the weekend. "He's got to be the most unselfish person I've ever met, the most caring person I've ever met, and also the strictest person I've ever met."

Though his roughly decadelong stint as Quaker City's music director ended in 1992, at age 55 Fox continues to march and to teach, and sees the fruits of his efforts all around him. "There are guys here who are probably 40 years old that I taught," he said. "And then there are kids who are 9 who I'm just starting out with now. It's been rewarding."

The club's current music director, Fran Rothwein, sees Fox's continued involvement as an invaluable asset to his own work. "He's so respected by so many members of the band," Rothwein said. "He taught so many of them. He taught me a lot about writing and arranging. He knows what I want from the band, and if I get pulled off in another direction Jimmy's not afraid to step up and fix things that he hears."

Fox followed his father into Quaker City's ranks in September 1967, marching for the first time on New Year's Day 1969. He later attended the Philadelphia College of the Performing Arts, one of the schools that later combined to form the University of the Arts. After college he went to work at the Naval Shipyard until its 1995 closing, after which he went to work for the Postal Service. He began taking on private students in 1981, the same year he became Quaker City's music director.

"He's a great teacher," said John Navickas, a Quaker City alto player who began studying with Fox in 1986, when he was in the sixth grade. "He made sure that you were playing the correct notes as opposed to how fast you could become a rock star. He was very supportive."

Though he estimates that the number of his students who have gone on to play in string bands is in the hundreds, with about 50 now marching for Quaker City and other bands, Fox insists that he doesn't push his students into the string-band route, concentrating instead on musical fundamentals. "I try to keep my lessons separate from string bands," he said. "You want to go to string band, that's fine, but you're going to be a sax player, not a string-band sax player."

Still, a majority of Fox's students found him through Mummers channels, via fathers or siblings who were part of a band, and the Mummers' repertoire did factor into his teaching. As Michael Brown recalls: "A string-band tune was like dessert. At the end of your lesson, you knew if you did well he'd reach into his briefcase and pull out a Mum tune. You'd look forward to that."

Fox is quick to point out the mentors who have preceded him: Bill Garton, a retired South Jersey public-school music teacher who was involved with the Fralinger String Band and taught Fox himself, among many others; and Herb Smith, Fralinger's music director emeritus, whom Fox credits with advancing the modern Mummers sound.

"Back in the 1970s," Fox said, "most of the harmonies were just simple block harmonies, and then Herbie started introducing swing. Fralinger did a big-band medley one year, and it was lights out in the string-band arena. Since then things have evolved, but that's really what made the saxophone the predominant instrument in string bands. Nowadays the qualifications are a little bit higher than they might have been 30 or 40 years ago."

His efforts have paid off beyond the sequins and feathers on New Year's Day. Fox's students have earned spots in All-State and All-City bands in Pennsylvania and New Jersey. He's proud of those accomplishments, but doesn't look down upon string-band playing, either.

"On Wednesday night one of my students will be playing 'Four Leaf Clover' and on Saturday he's auditioning for All South Jersey playing a Haydn sonata. That's a pretty wide range. A lot of people frown on string bands, but just like sports, you can take all the lessons you want, but until you get on the field and play, it doesn't mean a thing. This is a great avenue for young guys to play their instrument."

Fox's students range in age from 9 through high school, though there are Quaker City players in their 30s who insist they're still learning from him.

"He's become one of my best friends," said Brown. "If I need any advice or if I need to talk to anybody, he knows how to cut through all of the smoke and see the light at the end of the tunnel. He'll tell you to just be patient, take your time, and his music teachings were the same way."

In recent years, Fox has reduced his student roster from a high of 15 to about eight, citing the demands of juggling a day job, his "weekend warrior" stints with a band that plays weddings and banquets, and Quaker City rehearsals.

He's unsure how long he'll continue marching, but he has no plans to divorce himself from the organization as a whole.

"I love the camaraderie," he said. "You can see somebody in the band that's 15 years old talk with my 88-year-old father about sports. You don't see that a lot in other places in life."

For others, it's the draw of Fox himself that keeps them coming back.

"It's amazing the respect that the man gets when he walks into the room," Brown said.

"Whether it's people he's taught or people he's been friends with, or being in front of the band as music director, one of the reasons our organization is so tight is because of the circle of individuals Jim has touched over the years."