"You might say our band is a transition band arriving on the scene 50 years after the transition took place," explains Ed Fishel, who has occupied the piano chair in more Washington-area bands than he can count.

Fishel was trying to come up with a description of The Band From Tin Pan Alley, which he leads and which will be half of the bill for the Potomac River Jazz Club's monthly concert-dance tomorrow at the Twin Bridges Marriott from 8 p.m. until midnight.

"That name is not just a gag," Fishel insists. "It's a statement of musical policy. The Tin Pan Alley era was dated by some very round numbers: 1900 to 1950. The core of our book is the 250 or 300 biggest hits of that era. I couldn't find any authority to tell me what the biggest hits were, so I appointed myself.

"Our style -- and a better term than style is the spirit we play in -- can be dated pretty narrowly to the early and middle 1930s, when jazz bands were in transition from Dixieland to swing.

"At the swing end, we get as modern as 'Satin Doll' and 'Tuxedo Junction,' and we go up to early bop," Fishel explains. "At the other end, we go back to ragtime, spirituals, Jelly Roll Morton pieces. Also, we play those Dixieland warhorses -- 'That's a-Plenty' and the rest of the barn burners. But most of our book consists of pieces that are Dixieland and swing at one and the same time."

That book is arguably the most expansive, certainly the most eclectic, of area bands of this type. "We have about 360 pieces, and we can play 360 more without a chart, I suppose. If the situation is right, we put our play lists on the tables and play requests all night."

Fishel "first played this music for money" at a Catholic church in Harrisburg, Ohio, on New Year's Eve 1931. "I was just past my 17th birthday," he recalls. He went on to form a band at Mt. Union College in his hometown of Alliance, Ohio, and wrote arrangements for other bands. But Fishel's musical career was interrupted.

"I worked for the Cleveland Press the years I was in college, covering a couple of counties downstate . . . I was in music all that time, but when I got out of college I took a full-time job as city hall reporter on the local paper. There was a lot of night work, and for the next five years I just dropped out of music."

He was drafted in 1941, and a year later he found himself stationed in Arlington, where he put together a band; from that time he's been a force in the D.C. jazz scene. He graduated from playing piano in small groups to organizing a government agency band midway through a third career. He also has undertaken projects to further the course of the music he has loved for more than half a century. Among these was the organization of monthly jam sessions during the '70s, an effort that spawned half a dozen or so bands. As the Potomac River Jazz Club's first musical director, he put together a regular Sunday night series of local bands and compiled a musicians directory of local players.

"The last two weeks I was in the government trying to work off the contents of my 'in' box in 1972, I played 11 gigs in 14 nights with seven different bands," Fischel says, somewhat incredulous now at the memory.

(Alternating sets with Fishel's band tomorrow night will be Baltimore's Peabody Ragtime Ensemble, which last month appeared at the seventh annual Copenhagen Jazz Festival. For more information on tomorrow's event, call the Potomac River Jazz Club's hotline, 532-TRAD. The line gives a weekly update on area traditional jazz activities.)