For an a cappella group, a strong bass singer is every bit as important as a good lead vocalist. With no drums or string bass to carry the beat and anchor the bottom, the bass singer's deep, resounding scat syllables have to carry the weight. Fortunately, both of the a cappella male doo-wop groups at Anton's last night enjoyed the services of an excellent bass singer: Jimmy Hayes of the Persuasions and Jimmy Bethel of D.C.'s Finest. Oomphing like a Dixieland tuba, each singer provided the stomping ground beat that held the harmonies together.

The four living members of the original five Persuasions are still singing together after 27 years. They started out as a classic doo-wop group, but last night they equally resembled a Southern gospel quartet such as the Dixie Hummingbirds. With Hayes on the bottom, Jerry Lawson and Jayotis Washington sang the tenor leads, and Joe Russell supplied the stratospheric falsetto. They applied their distinctive blend of street-corner and church singing to an ambitious spectrum of material -- everything from Nat King Cole's "Mona Lisa" and Elvis Presley's "Return to Sender" to Johnny Horton's "The Battle of New Orleans" and Paul Simon's "Slip Sliding Away."

An unexpected delight was the unadvertised opening set by D.C.'s Finest, an a cappella quintet featuring three active-duty D.C. police officers and two retirees. In their opening number, Richard Collins promised that "Doo Wop's Gonna Get You," and he was quickly proven correct. The Persuasions and D.C.'s Finest perform at Anton's through Sunday.