Something new was added to the decor in the Mount Vernon College chapel for the latest production of the imaginative "In" Series: a small proscenium stage with scenery (by Dreama Greaves) depicting a street in the Lavapies neighborhood of Madrid.

Musical productions in this series tend to be minimalist in their sets. The performing space usually merges smoothly into the audience area, using a few props and costumes to establish the setting, whether the music is a Mozart opera or an evening of cabaret. But for the current attraction, an adaptation of the 19th-century zarzuela "El Barberillo de Lavapies" ("The Little Barber of Lavapies"), it was essential to establish a clear-cut boundary between audience and performers.

That's because one theme of the production--unlike any other staging this popular Spanish work has ever had--is the interaction between two "audience members" (actually star performers) and the characters onstage. You might say that this "Barberillo"--an intercultural production with dialogue in English and songs in Spanish--is about the transforming effects of a good theatrical experience: the intrusion of 19th-century Spanish passion into the lives of two present-day Washingtonians.

Friday--opening night--the show began before Music Director Angel Gil-Ordonez gave the first downbeat to his small "orchestra" (clarinet, violin, cello and piano): Two last-minute "patrons," Larry (Richard Tappen) and his wife, Marge (Laura Lewis), came barging in, loudly and disruptively looking for the last two seats in the sold-out auditorium. They finally found them, in the front row. Interaction began, just before the first songs and dances, when a character onstage passed a mysterious briefcase to Marge.

The zarzuela proper--the genre is part operetta, part vaudeville--begins (in Spanish) with a big production number involving flirtation between the male and female choruses. The leading zarzuela characters, the barber Lamparilla (Peter Joshua Burroughs) and the seamstress Paloma (Ana Castrello), introduce themselves in sparkling arias with the chorus, and the show seems well launched in traditional style until Marge ventures onstage, trying to return the briefcase, and soon starts to be transformed into a zarzuela character--complete, eventually, with a change of costume--singing in Spanish. After trying without success to bring her back to offstage "reality," Larry goes off to find a policeman while the show continues. When he returns with a D.C. cop (Darryl Winston), he barges into the zarzuela and suddenly finds himself singing in Spanish; he becomes a Spanish nobleman, a counterpart to his wife (who has become a Spanish lady). The policeman, who suddenly discovers that he can sing, becomes the captain of the slapstick Lavapies town guards.

The script, written by Elizabeth Pringle and very different from the 1874 zarzuela by Francisco Asenjo Barbieri and Luis Mariano de Larra, includes elements reminiscent of Abbott and Costello and the Keystone Kops, as well as the rekindling of a long-worn-out love between Marge and Larry. But it matters mostly as a setting for the quintessentially Spanish songs and dances and as a vehicle for the Pirandello-like theme of two interacting levels of reality: 19th-century Madrid and Washington today. The themes are summarized in a monologue by Larry: "A dream, this must be a bad dream. I don't even recognize myself. I can't wake up and I can't do anything here--except sing in a language I don't understand and chase people around with a bunch of cops who couldn't catch a cold. I have never talked to my wife this way! I don't know if I have ever felt this way. I'm a CPA, for God's sake, and I'm wildly in love. With my wife!"

The performers handle their complex assignments, under the direction of Tom Mallan, with verve and versatility; the music is splendid and the dancers (Debra Belo, Jaime Coronado and Nancy Sedgwick) greatly enhance the zarzuela dimension of this unique theatrical experience. There will be repeat performances Wednesday, Friday, Saturday and next Monday.

CAPTION: Dancers add vitality to "El Barberillo de Lavapies," though a staging twist makes this production notable.