The Preservation Hall Jazz Band has become almost as much of an institution in Washington as in the Crescent City. It has performed at Wolf Trap every year since that venue opened, bringing its highly stylized New Orleans repertoire to life in a swirl of bouncy syncopation that authentically recreates a style of jazz prevalent at the turn of the century.

It's a style that predates the rigidity of Dixieland, and it has much of the same insistence as the best ragtime. The melodies tend to be bright and friendly, essayed over a steady beat and lacking the superfluous embellishments that became standard in later jazz forms. Under the somewhat disciplined restraint of this classic form, though, there is a thoroughly irrisistable swing and a sense of joyful improvised harmonies.

"New Orleans, Vol. II" is a sprightly compendium of the band's own tunes and a couple of chestnuts, W.C. Handy's "St. Louis Blues" and "I Ain't Got Nobody." The elements are familiar to anyone who's seen the band: Josiah Frazier's parade style percussion, Narvin Kimball's buoyant banjo and Allan Jaffe's booming tuba bottom combining with casual urgency to propel everyone else along; Frank Desmond's gruff trombone tones and James "Sing" Miller's gutbucket piano strolls.

Most of all, though, the New Orleans sound is contained in the work of brothers Percy and Willie Humphrey on trumpet and clarinet; even in their 70s, they can growl and moan and stomp and be blue, and Percy can recreate that almost mumbled Bayou vocal growl made familiar by Louis Armstrong. Sometimes, the ensemble work drags, but it's almost always revived by an exuberant and heartfelt solo. These gentlemen are a living tradition and a piece of Americana that's all but disappeared. ON RECORD, ON STAGE THE ALBUM: Preservation Hall Jazz Band, New Orleans, Vol.II (CBS 37780). THE SHOW: Sunday at Wolf Trap.