The Philadelphia Dance Projects this weekend is reviving dances that date back 30 years. From WHYY’s Arts and Culture desk, Peter Crimmins reports dance is one of the most difficult art forms to preserve.

Think about it. Symphonies can be rendered as sheet music, captured on recordings. Plays have scripts, operas have libretto. But a dance performance; how do you preserve it, unless you have videos, which tend to be few in number and prone to fading.

Back in 1980 Dan Martin collaborated on an experimental dance with two partners. It was about gay liberation, they dressed in polyester parachute pants – when they were dressed at all. It was cutting-edge stuff.

Martin: It’s was very much of its time. It has the late 70’s woooooo sort of environmental sound.

It seemed like a good idea at the time. They still think it’s a good idea, if a little dated. Martin says they are lucky that video exists.

Martin: We have this one video of this piece – but we have a whole body of work that’s lost – no tapes of earlier pieces. We have early documents of reviews – our journals and notebooks. Other than that, they are gone.

Terry Fox says Philadelphia’s rich dance history intersects with its political history. She recalls her friends commandeering a vacant lot at 10th and Wood Streets in 1979, and building a massive stage set.

Fox: It was the Vine Street Expressway coming through, it was stalled with neighborhood protests. Those vacant lots were good opportunities for artists to set stage.

Librarian Tom Whitehead is spearheading a dance archive at Temple University. He says video is the best way to record dance for posterity, but in the 70’s video was hard to come by.

Whitehead: There’s a lot of personal hand-held cameras. Not professional. But for many companies – Pennsylvania Ballet, for instance, you find more professional taping.

Even professionally shot tapes disintegrate. Both Terry Fox and Tom Whitehead face the daunting task of digitizing material from a a half dozen obsolete video formats. And in 20 years, someone will have to update it again to a different format.