The New York Post reports that box-office sales for the Kander and Ebb musical have spiked ever since it was announced that the R&B singer-songwriter will join the Tony-winning revival Aug. 22. Usher is slated to play slick lawyer Billy Flynn through Oct. 1. The New York daily also says there is a possibility Usher may extend his limited engagement for an additional four weeks.

Chicago producer Barry Weissler told the Post that ticket sales for the musical are up 30 percent, with the box office taking in as much as $100,000 a day, quite a remarkable figure for a musical that will celebrate its tenth anniversary in the fall.

"We weren't doing anything at all for the period he's going into the show,” said Weissler, “but that shot up immediately. . . . It's not gigantic yet, but I'm pleasantly encouraged." A spokesperson for the musical told Playbill.com that advance sales for the show are "growing by the day — both at the box office and [through] Telecharge."

Usher will follow a long list of celebrities who have played the ultra-smooth Billy Flynn, including George Hamilton, Huey Lewis, Wayne Brady and John O'Hurley. The role was originated in this revival by James Naughton, who won a Tony Award for his performance.

Usher is a five-time Grammy Award-winning artist. His fifth album, "Confessions," was released in 2004 and sold over 15 million copies. The Hip-hop artist has also appeared in such films as "She's All That," "The Faculty," "Light it Up," "Geppetto," "Texas Rangers" and "In the Mix." His television credits include "The Twilight Zone," "7th Heaven," "Moesha" and "American Dreams." Chicago will mark Usher's Broadway debut. Chicago currently features Brenda Braxton as Velma Kelly, Rita Wilson as Roxie Hart, Obba Babatunde as Billy Flynn, Kevin Chamberlin as Amos Hart, Lillias White as Matron "Mama" Morton and R. Lowe as Mary Sunshine. Michelle DeJean will step into the role of Roxie Hart Aug. 8-20. Bianca Marroquin, who starred in the Mexico City production of Chicago, will begin performances as Roxie Aug. 22.

Chicago won the Tony Award for Best Revival of a Musical in 1997 as well as awards for actors Bebe Neuwirth and James Naughton, director Walter Bobbie, lighting designer Ken Billington and choreographer Ann Reinking. The original production was directed and choreographed by the late Bob Fosse.

Chicago plays the Ambassador Theatre, located at 215 West 49th Street.