"I'm thrilled to death with these players. And I don't have to con them into it. They all want to do it because it's a challenge and it gives them a chance to be a civilian for four hours," says Bill Potts of the dozen and a half musicians, all but one or two from the area service bands, whom he puts together every few months for a performance.

The Bill Potts Big Band will be at Blues Alley tomorrow night. And among the charts they'll do will be Potts' compositions "Momsville," "550 Feet High" and a piece he wrote for Buddy Rich, "Big Swing Face."

Of all the behind-the-scenes persons who contribute to the sounds of large-ensemble jazz, the arranger-composer is the most important. Potts has written for, to name only a representative few, Count Basie, Benny Goodman and Stan Kenton.

Potts went to Arlington's Washington-Lee High School and into the Army band in 1949. After his discharge from the Army, he played area jazz clubs with his trio (saxophone legend Lester Young was guest player for several weeks) and led the local The Orchestra with which, on occasion, Charlie Parker, Dizzy Gillespie and others were featured soloists. He now lends his skills to students at Montgomery College, in Rockville, where he has taught arranging for a decade and periodically pulls his tapes of young Parker and Gillespie out of his closet for release on major labels.