BETHLEHEM, Pa. -- Outside Liberty High School, the school's baseball players practice and its track athletes race.

Inside the large, modern windows of the school's gleaming new band room -- isolated by some serious soundproofing, sealed windows and lightly toasted by the building's overactive heating system, which insistently warms the room on an otherwise mild day -- band members gather for practice.

But most of the musicians are older than your average high school student, some by several decades. And despite the room's heat, everyone seems upbeat, happy to be seated before sheet music on music stands on an otherwise sunny day in Bethlehem, just northeast of Allentown.

The gathering is the twice-monthly rehearsal for one of the Lehigh Valley's more unusual alumni groups, the Liberty High School Alumni Band. Where other alumni gather to share food or tailgate before football games, these band members, most but not all actual alumni of the high school, meet to perform the marching band music they played before they received their diplomas.

The band was prepping for its final concert of the year, a gig in early May with the Easton Municipal Band, the alumni group's traditional season finale.

The band formed -- or reformed, if you will -- in 1991 when some former band parents approached the just-retired director of the Liberty High School Band, Ron Sherry, and asked if he might consider leading an alumni group.

There were two immediate reasons to regroup. The city of Bethlehem was celebrating its 250th anniversary, and the school's award-winning Grenadier marching band, which Mr. Sherry had established, was scheduled to perform outside the city.

Carol Mark, a longtime Liberty High School band mother, quietly approached other band parents and some recent grads with the idea of reforming the group for the city's anniversary event. She also checked with the school's principal at the time, who supported the idea.

Mr. Sherry had just retired after almost 30 years as band director at Liberty. He took over the band in 1961 and by 1966, transformed the group, and changed the uniforms, modeling it after a famous British marching unit, the Coldstream Guards, a move that helped the band achieve national and international acclaim.

"Before I talked with Mr. Sherry, I made sure all my I's were dotted, all my T's were crossed," recalled Ms. Mark, whose son Sam played percussion in Liberty High School's band. "I even spoke with his wife and she put in a good word for us. She sort of paved the way."

Mr. Sherry recalled the approach and his reaction. "Well, I was sort of hesitant. But a lot of coaching from many people and from some key musicians got me over the hump. At first, we just got together to practice. I wouldn't let them play any concerts. We just met and played music together for the next two years. But before you knew it, other people who were not really alumni were joining the band. They just came from all over."

The first rehearsal call suggested the loyalty former members hold for the band and its conductor. Mr. Sherry optimistically figured around 100 former musicians, or "bandos," as the members proudly call themselves, would show up, but more than 350 attended.

About 300 eventually became members of the alumni marching band Mr. Sherry assembled and a similar number for a concert band. "They were from all over the place, from 14 different states, representing 56 different graduating classes of Liberty High people," Mr. Sherry recalled.

A marching and a concert version of the alumni band performed, respectively, at the opening and closing ceremonies of Bethlehem's 250th birthday celebration. After that, Mr. Sherry expected interest to wane. It didn't. After several years of practice, the group formed its formal concert band in 1995. The concert version -- the group hasn't marched in years -- is celebrating its 15th year.

Not only did enthusiasm increase, the musicians insisted that Mr. Sherry be as demanding on them as he was during their high school days. "The band really wanted him to work with him and get better," said Ms. Mark. Many of the older members had not played in years.

The successes the alumni had as members of the high school band motivated many to resume playing. As Grenadiers, the members performed in Thanksgiving Day parades in New York and Philadelphia, traveled to the United Kingdom to perform with the Coldstream Band in London's Royal Albert Hall and hosted the Coldstream group when they visited the United States.

They also were a fixture at local parades and dedications. After several wins at a prestigious Florida marching band competition, the city of Bethlehem named a street near the high school after the group.

Mr. Sherry's time with the band was the main reason why the Bethlehem Chamber of Commerce decided to present the band leader with the Priscilla Payne Hurd Award at the group's annual dinner on May 12. The award recognizes individuals who improve the city through the arts.

"Bethlehem has this unbelievable tradition of strong high school and middle school bands and, I would venture to say, healthy elementary school bands," says Lynn Logue, a chamber officer who played flute in both the Liberty High School and alumni bands. "I fully believe it all started with Ron Sherry."

If Mr. Sherry was sometimes intimidating to high school students, he is much more low key with members of the alumni band, says Ms. Logue, who as a student thought Mr. Sherry "was kind of scary. You didn't want to make him made angry."

At a recent rehearsal for the alumni band, Mr. Sherry offered equal measures of encouragement and direction.

"Let's just cruise through this so we get it right," said Mr. Sherry as the band is about to play a John Philip Sousa march, "Ancient and Honorable Artillery Company." (Sousa marches are a band specialty and the band typically performs two Sousa concerts each year.)

But Mr. Sherry also is quick to acknowledge his own rehearsal mistakes.

As he stopped the group with a subtle wave of his hand to review a section of music, he asked them to resume playing at a different spot. Several band members remind Mr. Sherry where they actually stopped. "I completely missed that," he said.

"When I agreed to this, I decided this was going to be fun. Our motto is 'Having Fun Playing Good Band Music.' If you missed a couple of notes, you'd get them next time. And I think that's why the group is so successful. People have fun."

Having fun is a thread that connects the band members, which include some current Liberty High School student musicians.

"I just love being here," said Jen Kerchner, 18, a Liberty graduate who studies music education at Bethlehem's Moravian College. "It's fun music and fun people. It's not something I'm required to be in, so I like being here."

The current group numbers about 85 people and includes several pairs of fathers and sons, and even one grandfather and grandson combination: Warren A. Wilson, a trombonist who has played in the Allentown Municipal Band since the 1960s, and his grandson, Josh, a Liberty junior, who also plays trombone.

"It is just fun because all the other organizations I play in are really more serious, more performance oriented," said the younger Wilson. "When I get to come here, it's really fun because I get to play with my grandpa and I've looked up to him since I was able to go to West Park and watch him play for the Allentown band."

Mr. Sherry, 76, expects to continue conducting the band for several more years. "As long as I enjoy it and have a good time, I'll keep doing it. It has been very easy for me. You run into little problems, little conflicts with other things going on in the community, but so far, they've all been minor. I have some pretty good players. I've been blessed with this."