THE SUNDAY MORNING BAND -- Monday night at Blues Alley.

Big bands. Sultry saxes, scorching solos, colorful choirs of brass. This Monday, one of the area's hottest big bands, the Sunday Morning Band, moves down from its weekly gig in Rockville for a night at Blues Alley.

The arrangements of leader Mike Crotty allow for an unusual amount of free soloing while keeping the tight unison feel that makes a big band come across as a single, overpowering instrument. The combination demands exceptional musicianship, and, not surprisingly, all but a couple of the members are full-time musicians who keep themselves busy with studio work and other groups, and play in the Sunday Morning Band primarily for fun.

Big bands are hard to support financially, and though this one's been around for four years, appearances have been none too frequent. Crotty, who graduated from Boston's Berkely School of Music with a degree in composition, started the band after coming to Washington to write charts fro the Air Force jazz band. With a nucleus of Catholic University students and several Airmen of Note, he began regular Sunday-morning rehearsals of his arrangements.

Their first performances at Frankie Condon's club, in the Rockville Plaza Motor Hotel, grew out of casual conversations; Condon's a big-band fanatic who books jazz bands six nights a week -- including, on Thursday nights, his own 15-piece dance band. For the past 15 months, it's been Sunday Morning on Monday nights, and every other week the band features a guest soloist, local or visiting.

The Blues Alley appearance will be the band's biggest step to date toward wider exposure, and Crotty has plans for more intown performances and, perhaps, a live album. But no forays out on the road: "If it stopped being fun," he says, "there wouldn't be any more band."