The public often mixes up Salt Lake City's two long-established modern-dance companies -- Repertory Dance Theatre and Ririe-Woodbury Dance Company. On paper, they might look similar -- both were founded in the mid-1960s, have similar-sounding names and produce consistent seasons at the Jeanné Wagner Performing Arts Center with professional contracted dancers. To add to the confusion, RDT and RW are modern-dance repertory companies.

Due to its very nature, pinning down a definition of modern dance in 2010 is futile. The search for an accurate term for modern dance after its inception -- through the postmodern era of the 1970s and the post-postmodern era through the 1990s -- got so clumsy that definitions defaulted to specific approaches, such as "contact improvisation" or "release technique." But as Twyla Tharp said, when describing modern's inclusivity of all dance traditions and its openness to personal interpretation, "Modern dance is not less, it is more." That philosophy is why the dance world has settled on the inclusive label of "contemporary dance."

And since "repertory" is Latin for "storehouse," a rep company is one that presents from a collected catalog of works, usually in alternation. On the national scene, non-rep companies include Paul Taylor Dance Company (1930-) and Martha Graham Dance Company (1894-1991), which exclusively perform the founder's body of work.

RDT performs new and commissioned works, while R-W is now the only company in the country to produce full evenings of Alwin Nikolais (1910-93).

What distinguishes RDT from other rep companies is its commitment to preserve modern dance history. Since 1966 when the Rockefeller Foundation designated and funded RDT as a "museum," the company has built a living archive of American modern dance. In October 1980, company dancers appeared on the cover of Smithsonian magazine, known for its coverage of history, the arts and world culture.

Being a museum of dance is more complicated than a library of books or temperature-controlled rooms of paintings. The invention of video, DVD and motion-capture technologies makes recording dance easier, although some choreographers still insist on using a system invented in 1928 by Rudolph Laban called Labanotation. This archiving method starts with a deceptively simple stick figure and adds symbols notating every detail from direction to effort to intention.

"Last year, choreographer Ze'eva Cohen notated a piece so it would be exact," RDT artistic director Linda Smith said. "But we usually use video and a series of carefully documented notes."

Smith said the company videotapes dancers from above, below and all sides. They document choreographer corrections during rehearsal and, afterward, dancer comments about sight cues, as well as other details cameras can't perceive.

"I compare it to the 44 years of costumes we have in the basement," Smith said. "Dancers today are different. They move differently, their bodies are shaped differently and no matter how well you document, dancers are going to perform the dance differently -- and you're going to have to buy new costumes."

Because dance is an ephemeral art form, what can and should really be preserved?

Historic works serve as "a snapshot into the particular time and culture," said choreographer Stephen Koester, an associate professor of dance at the University of Utah. "As in the other arts, the lesser works tend to disappear while those works which either changed the art form or were perfect in their genre survive."

Modern dance is less than 100 years old, and names such as Isadora Duncan (1877-1927) or Merce Cunningham (1919-2009) are recognizable.

So in 2009, when RDT received an American Masters grant by The National Endowment for the Arts to become the repository for preserving the legacy of Michio Ito, the $120,000 award raised the question: Who is Michio Ito? And if he is one of the early modern masters with Graham, Doris Humphrey, Ruth St. Denis and Ted Shawn, why don't dance lovers know about him?

"That is what is so wonderful about preserving work," Smith said, "we can return a master to his rightful place. Being Japanese in pre-WWII America, Ito was in the wrong place at the wrong time in history and before he could make his mark, he was imprisoned and deported."

Ito (1893-1961) created dances based on a sparse 10-movement vocabulary. "His work stems from a time when instant communication did not exist, and small changes were dramatic," said RDT dancer M. Colleen Hoelscher. "I believe it is the simplicity that makes his work so raw and stunning."

Two other works on the program contrast with Ito's since they are "fast-paced, complex pieces full of intriguing movement and delicious human interactions," Hoelscher said. One is by Norwegian choreographer Jo Stromgren and the other by Satu Hummasti, an associate professor in the U.'s modern-dance department. Also on the program is Ze'eva Cohen's 1985 Greek myth-inspired piece, "Ariadne."

Maybe by its very definition, every repertory modern concert should be full of contrasts, encompassing the yin and yang of life. "It's a great reminder to stop and smell the roses," Hoelscher said, "while sipping a triple shot, extra hot, half decaf, nonfat, vanilla, extra foam latte."

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