Vehicles breaking down, musicians stranded along the road, arrival barely in time to struggle into uniforms and mount the bandstand. A 1930s big band tour? No, just another day in the life of the McLean Jazz Workshop and its two 25-piece orchestras, composed of 9- to-17-year-olds. The workshop will give its spring concert Friday at 8 p.m. in the Alden Theatre of the McLean Community Center.

"We go from traditional big band through contemporary jazz-rock fusion," explains workshop director and founder Jeff Cummins, who plays piano and saxophone with local jazz groups. The concert program will draw from the books of Duke Ellington, Count Basie, Woody Herman, Maynard Ferguson, the Doobie Brothers and others.

The workshop began three years ago as a part-time summer activity and now meets weekly all year and daily during the summer. It was for high schoolers initially but soon "a lot of little brothers and sisters started popping up," says Cummins. The bands have played at Wolf Trap and the Kennedy Center, on local radio and TV, and for schools, orphanages, nursing homes and homes for the retarded throughout Virginia. Last year they were invited to perform at the World's Fair in Knoxville, Tenn., and this summer they will play at the Fort Monroe, Va., Fourth of July celebration.

Cummins, who will be named McLean musician of the year Saturday, which is McLean Day, observes "the idea is that the workshop is a neat place to be and it beats heck out of catching kids in the parking lot in the middle of the night."