Edna Gordon, 38, shopping bag in tow, approached the construction tunnel at Eighth and I streets NW from the north, stepped inside and heard the sound of a harp and galloping hooves. Gordon broke into a big smile.

As she proceeded the length of the tunnel, other sounds joined in: Bells, birds, was that a banjo? By the time she reached the end, Gordon was laughing.

"I didn't know, I didn't know anything about it," she said. "It sounds nice to me . . . . I think it's very entertaining."

A few minutes later, along came Henry Sanchez, 15. When the sounds started, Sanchez looked around puzzled. "What's happening in here, what's with this music?" Sanchez asked. "It's nice, fine, but where is it coming from?"

It looks like a regular tunnel skirting a construction site: flimsy plywood walls, screened cut-out windows, the roar of construction crews pressing in from either side, people rushing to get through.

But once inside, the tunnel comes alive with the sounds of the jungle, both urban and the other kind. It's SONIC PASS/dc, an urban sculpture designed by Washingtonian Christopher Janney.

The project was commissioned by International Developers, the builders of Techworld Plaza, which is under construction at Eighth and I streets.

"The concept of Techworld is to provide a stage for anything in advanced technology, so we are looking for this kind of thing," said Guiseppe Cecchi, president of International Developers and the builder of the Watergate complex. "We were also trying to make something interesting out of this passageway."

Janney, trained as an architect and musician, said SONIC PASS/dc combined the best of both disciplines. "This sculpture is a way of putting spontaneity into architecture, while also giving music a physical manifestation," he said.

Two weeks ago John Young and nine other seventh-graders from the National Learning Center were invited to be the first people to walk through it at the official opening.

At first, the premiere appeared to be a typical field trip. It was hot and muggy. It was kind of boring, he said.

Finally it was time to walk through the 20-yard tunnel where the effect of people passing eight small holes about a foot off the ground breaks a beam of light and triggers computers hooked up to play music. The sound of harps, flutes, bells, crickets, birds, and assorted city noises fills the tunnel.

Janney had the kids run through the tunnel, and the music went faster. Then he had them stand in front of the beams and swing their legs , controlling the sounds.

"You're looking at this construction site, but you're hearing like you're in a rain forest," said Janney, now an artist-in-residence at the Massachusetts Institute of Technology.

Well, maybe. The kids heard the music based on their own experience. "It reminds me of that stuff off the 'Karate Kid,' " said Young.

"Sounds good, like Chinese music," said Thelma Bautista, 14. "If I was walking through here and was surprised by the music, I'd feel great, because it sounds like some birds are singing to you."

Not Adrian Smarr, 14. "If I just walked through here and heard this music, I'd think something was going wrong," he said."

After several weeks, SONIC PASS/dc became old hat to many of the construction workers and people who walk through it to work in nearby office buildings. But not everyone.

"I think it's pretty neat, actually," said Tom Cohen, a technician who walks through the tunnel about five times a day.

"I like it," said Ednina Dodson, who works at the Ramada Hotel. "It's like a soothing kind of sound. I play with it a little," she admitted with a grin, swinging her leg back and forth in front of a beam of light.

Then there are those like Edna Gordon, who happened upon SONIC PASS/dc on her way to find a job and, captivated, made a point of walking through again on her way back. "I just love this," she said. "I am going to bring my grandson, Marrice, down here. If it wasn't raining, I'd bring him today."

SONIC PASS/dc will remain in place for about a year. The sculpture will operate 20 hours a day, seven days a week. It is closed from 2 a.m. to 6 a.m.