WESTBROOK, Conn. -- The August afternoon at Ted Lane Field is so sweltering that people are walking behind the bleachers and standing under the two open showers fully clothed.

An overnight rain has done nothing to cut the humidity or to keep down the dust as corps after corps exits the parade route and marches onto t he infield. As uncomfortable as it is for us waiting in shorts and T-shirts, it must be near torture for the musicians in their woolen uniforms, historical hats and knee-high boots.

It's the 50th Annual Westbrook Drum Corps Muster in Westbrook, Conn. We're close enough to Long Island Sound to hear the roaring jet skis, but the sounds coming from the Little League field are not nearly so modern.

They're the living tradition of a centuries-old style of fifing and drumming that once summoned the colonists against the British. We may have borrowed fighting techniques from the Native Americans, but our military music hearkens back to a European past.

Virtually every weekend throughout the summer in New England, these "musters" call together dozens of corps and, as one old poster put it, "all who thrill to the shrill of the fife and the thunder of the long drum."

It seems like almost every small town out here has its own corps -- a unit of 10, 20 even 40 musicians, from elementary school children to 80-somethings, who study fifing and the traditional rudimental style of drumming, learning as many of the military airs and marches as their free time permits.

Along Westbrook's Main Street on a warm Saturday morning, families have already placed their chairs under giant shade trees at 8:30 a.m. for the 11 a.m. parade. Volunteers are setting up a church bazaar on the nearby village green. Thousands will watch the parade, and hundreds more will attend the subsequent, more formal musical presentation -- the muster -- on the ball field.

Though enjoying the "ancient fife and drum" style of field music seems to be an exuberant undertaking for residents and tourists, passing along the musical knowledge has become, in recent years, a family affair. Interest waxes and wanes in strange cycles that seem to correspond to war, hard times and historical watersheds.

Going through the Museum of Fife and Drum in nearby Ivoryton, I noticed that the nation's oldest corps were founded a few years after the Civil War ended. Some of the corps held annual musters, or "field days," but rivalries between the corps were so intense -- and rancorous, it seems -- that they stopped holding these competitive events.

Just after World War II, participation surged and the musters resumed. Their motto now? "No judges, no prizes, no unkind words." Growth continued straight through the 1960s and peaked with the nation's Bicentennial celebration in 1976.

Was it ex-soldiers seeking camaraderie in peacetime who galvanized corps growth? As we move into another post-war period, could this still-healthy tradition grow stronger?

Museum curator Jim Clark, who leads and arranges music for three vibrant corps, thinks it has less to do with post-war pangs than economic hard times. A drum pad and pair of sticks are cheap, as are fifes, and a whole generation of truly terrific musicians grew up during the Great Depression, he said.

They in turn taught thousands of youngsters who flocked to the corps during the '50s and '60s. Today they're keeping the music alive -- and through it, American history -- as old tunes blend with increasingly funky rhythms, and as some units boast almost as many women as men.

Just a few of the corps you'd drop everything to go see: the Ancient Mariners, the (all-black) Charles W. Dickerson Field Music, Connecticut Valley Field Music, Stony Creek Fife & Drum Corps, and of course "The Old Guard" from the U.S. Army's Third Infantry Regiment.

For most, this is not a costumed escape into a fantasy of the past. It's about music, community and heritage -- and the next generation of fifers and drummers exchanges woolen duds for bikini tops and shorts in a flash.

Three- and four-hour-long jam sessions -- with hundreds of musicians playing the same jigs and reels all together -- unfold each night till curfew, but the party continues, in and out of the scores of tents and campers that crowd the adjacent ball field, till Saturday has long slipped into Sunday.

We stayed miles from the action but stopped by the field on our way out of town early Sunday morning. For the first time all weekend, things were very quiet.