WHAT HAPPENS when you put together one of Washington's best jazz musicians, an excellent rock band and a burlesque entertainer whose singing bears only the most tenuous connection to pitch and rhythm? Why, you get the latest Root Boy Slim album: "Don't Let This Happen to You!" While the musicians play hard-rock, doo-wop and jazz-funk flawlessly, Foster "Root Boy" McKenzie grunts and growls about romancing zombies and robots.

Sometimes this can be rather funny in a Mad Magazine sort of way. As the band plays a jazz-rock groove, McKenzie grumbles that he's lost his woman to a "Computer Lover" program with better bedroom technique. On the Springsteenish "Date the Undead," he hoarsely lures a young groupie in into his grave. And in his next song he unveils the new national anthem, "Rich, White and Republican."

On Side Two, McKenzie tries to get somewhat serious and soon grows tiresome. "Murder One" is a pious commentary on American violence salvaged only by Ron Holloway's blistering sax solo. On "They Don't Sing on the Corner," McKenzie's monologue rambles on about the old doo-wop groups and the lousy new music with no sense of irony. Despite the hot solos by Holloway and guitarist Ernie Lancaster, the songs are only as good as the jokes, which only work half the time.

ROOT BOY SLIM -- "Don't Let This Happen to You!" (King Snake 001); appearing Friday at the Roxy.