Like discovering a chocolate chip in a piece of pound cake, visitors making a summer pilgrimage to this "city beautiful" founded by Joseph Smith are apt to encounter an unexpected treat.

The treat is "Nauvoo Adventure," a musical production presented in the theater at the Church's Visitors Center. Featuring 12 well-scrubbed, college-age Latter-day Saints, the production extends each year from Memorial Day to the Labor Day weekend."We call them our `performing missionaries,' " said Sister Evelyn Ricks, a missionary at the center, regarding the 12 cast members. Her husband, Elder Mark G. Ricks, is director of the visitors center.

In fact, Elder Ricks noted, some of this year's cast have received mission calls already, while others soon will be submitting papers pursuant to mission calls. One is a returned missionary.

"Visitors can't get over how fabulous the production is," Elder Ricks remarked, mentioning scores of visitor comment cards praising the show. "It gives a musical history of Nauvoo, and the people actually feel the Spirit. They feel they become better acquainted with the people and conditions 150 years ago."

An estimated 30,000 people saw the program this year by the time it closed on Aug. 31. It was popular enough that matinees were added to the performances.

In 75 minutes of singing, dancing and narration, the young people recount the 61/2-year period from 1839 to 1846, during which the Saints settled, built and then were driven from Nauvoo. Dressed in basic period costumes with no scenery and only chairs as props, they enact numerous scenes relating such stories as family separations due to mission calls, the martyrdom of the Prophet and the "Whittling and Whistling Brigade" of boys who kept an eye on unsavory characters in the city.

This year, in commemoration of the sesquicentennial of the exodus, author and creator Nonie Sorenson revised the show to include 20 minutes about the 1846 Iowa portion of the Saints' trek. One poignant scene is told from the standpoint of Patty Sessions, a midwife who went several miles each day up and down the wagon train to deliver babies. A line from her journal is included: "The sun came out today and dried our clothes, but my tears will not dry."

During their summer in Nauvoo, the young cast members do more than perform. "I have them serving in the restored historic sites," Elder Ricks said. "They dearly love that. They do an excellent job of giving tours."

"I've had many, many opportunities to bear testimony," said Tamsen Dunning, a cast member from Fort Collins, Colo., "I've been able to bear my testimony through singing, but also at the sacrament meetings we've visited and one-on-one with people of many different religions at the historic sites." She said it can be a bit frightening, "but a testimony is so personal, who can go against it? It's something no one can take away from you."

For Jeremy D. Harvey of South Ogden, Utah, his participation in the production is a tribute to his sister. Her friend saw the show last summer and told her about it. "My sister pushed me and pushed me to try out," he said. "I auditioned in January, and one week after the tryouts, she died. Just a little bit after that I found out I made it, and I kind of felt like maybe she had something to do with it on the other side. Through a lot of prayers, I know that this is what I am supposed to do."

Like many good things in the Church, the show originated spontaneously. In 1988, Sister Sorensen, a veteran playwright, went on a mission, during which time she revised the production "Nauvoo Rendezvous," presented by senior missionaries at the Cultural Hall, one of the historic sites. Her husband, Maynard, called to serve as a missionary doing wood sculpture in the Cultural Hall, suggested that the theater in the Visitors Center would lend itself to his wife's talents.

She wrote the music and narration and, through a series of events she called miraculous, was able to cast it in time for presentation that summer. One cast member, for example, was Bill Myers, a Methodist minister who taught drama at a Catholic school in town. Not only did he attend all the rehearsals, but he scrounged lighting from various churches with which he was acquainted.

For nine years now, the show has continued. Classified ads announcing auditions are placed in college and university newspapers. This year, more than 100 tried out for the six female parts.

Sister Sorensen, who recently moved into the Ivins 4th Ward, Ivins Utah Stake, in southern Utah, played the music on a grand piano for the first four years, and on a synthesizer for a couple of years. Since then, the synthesized orchestration has been recorded on tape, and the cast members sing live to it, without the aid of microphones. The taped accompaniment was upgraded this year.

She is pleased that the experience seems to be a fitting prelude to a mission for many of the cast. Most of the young men go on to fill missions.

And, she added, it's quite surprising how many of the young women from the group are going on missions.

Sister Sorensen said more information about auditioning for the musical may be obtained by writing Nauvoo Musical Theater Production, 50 E. North Temple, Salt Lake City, Utah 84150.