The fifth season of the "Musicals in Mufti" series at Off-Broadway's York Theatre Company will feature Darling of the Day, Kelly and Billion Dollar Baby.

Like City Center's "Encores!" series, "Mufti" casts an eye on neglected musicals through concerts stagings.

The Jule Styne-Yip Harburg-Nunnally Johnson Darling of the Day (Sept. 11-13) leads off the line-up. This 1968 musical is set in England in first decade of the century, where a celebrated painter escapes his success by assuming the identity of his deceased butler. Michael Montel directs.

Kelly (Sept. 18-20) comes from the same time period as Darling, 1967, and is also set at the start of the century. The Eddie Lawrence-Moose Charlap tuner is about a brash teenager -- modeled after 19th-century New York legend Steve Brodie -- who decides to jump off the Brooklyn Bridge on a bet. Donna Kaz directs.

Billion Dollar Baby, of 1945, was Betty Comden and Adolph Green's first project after On the Town. Morton Gould wrote the music. The musical follows the rise of a 1920s golddigger who climbs to the top only to get a shock at the end of the show. B.T. McNicholl directs. All the concerts are performed at York's home in The Theatre at Saint Peter's Church in the Citicorp Center (Lexington Ave. and 54th St.). Audience discussions follow matinee performances. For information, call (212) 935-5820.

--By Robert Simonson