ARLINGTON, Va. — A festival of John Kander and Fred Ebb tuners without “Chicago” or “Cabaret”? Unthinkable.No, it’s precisely the point. Signature Theater last week launched a four-month celebration of the works of Kander and Ebb that will include full productions of two musicals most auds have never seen: 1968 tuner “The Happy Time,” considered K&E’s lost musical; and “The Visit,” a reworked 7-year-old Terrence McNally-scripted project with Broadway aspirations. Opening attraction, which began previews March 11, is the more widely produced “Kiss of the Spider Woman”; however, the gritty show has seldom been staged by nonprofit theaters. The fest, which runs through June 22, is the biggest theatrical event in the history of Signature, which moved into a new $16 million facility last season. “Spider” and “Visit” will play the 299-seat Max Theater, while “Happy Time” is slotted for the 120-seat Ark. “Happy” will partially overlap the other runs, so people can catch two shows over a weekend. It is also the first such retrospective held that features the prolific collaborators, currently repped on Broadway by “Chicago” and “Curtains.” Kander is lavishing attention on the exercise, attending dress rehearsals and tinkering with the final products where necessary. Lyricist Ebb died in 2004. Kander will also participate in a May 12 one-on-one sesh with Signature a.d. Eric Schaeffer. Other events include a weeklong gig by cabaret singer Karen Akers, performing from the K&E songbook (March 11-16), Monday night screenings of four films based on the duo’s work, a week of contemporary dance perfs by Bowen McCauley Dance Company (June 12-15) and an exhibition of K&E memorabilia. A gaggle of performers with established Broadway credentials has been inked for key roles. In “Spider Woman,” Will Chase plays political prisoner Valentin opposite Hunter Foster as his gay cellmate Molina, with Natascia Diaz in the title role.Schaeffer has staged the 1993 Tony winner on an enormous and forbidding jail set. Michael Unger will direct “Happy Time,” featuring George Dvorsky, David Margulies and Michael Minarik. The production will reflect revisions made by Kander and Ebb in 2002, as well as more recent changes aimed at tightening the show, about a prodigal son who returns to his bickering Quebecois family. The May 13-June 22 production of “The Visit” will star Chita Rivera (the original Spider Woman), George Hearn and Mark Jacoby. Based on the Friedrich Duerrenmatt play, the $1 million show, which accounts for half of the festival’s budget, looks set to draw the lion’s share of national attention to the event. A substantially reworked version of the 2001 Chicago production will again be staged by Frank Galati and choreographed by Ann Reinking. Rivera plays a wealthy woman who returns to her hometown to avenge an ex-lover (Hearn). Jacoby will reprise his performance as the town’s mayor. The show has undergone substantial rewrites, including a new song each for the Rivera and Hearn characters, and a reconceived warehouse set. The dark, edgy play is receiving additional development and rehearsal time in New York. Schaeffer says advance sales are so strong that the entire six-week run likely will sell out before opening night — a first for the theater.