Andrea Brook and the Sonic Butterfly.

A unique, free concert experience will be staged in central Iowa next week featuring what’s known as a long-string harp with strings that will extend across a downtown Des Moines street, from a rooftop to a park below.

Andrea Brook is the musician who will be playing the instrument she calls the Sonic Butterfly, a 26-string acoustic, chromatic harp — though she says it doesn’t sound like a traditional harp as you don’t pluck the strings. “Because it’s a harp, each string is just one note,” Brook says. “I run my fingers along the strings, much like you would run your finger around the edge of a crystal glass, creating a longitudinal vibration, and this creates this really beautiful, very cello-viola sound.”

Brook is based in Ojai, California and she’s taken the two-octave instrument she designed to perform in countries around the world. This will be her first Iowa appearance. “I have strung the Space Needle in Seattle, the Grand Theatre in Shanghai, a mountain peak in Malibu, cathedrals in Mexico and Brazil, and many, many other spaces,” Brook says. “I literally run the strings from the stage, out at minimum 60 feet but maybe as far as 1,000 feet, and attach them to whatever it is that I’m transforming into the instrument.”

The harp has two resonating chambers that are shaped like butterfly wings, each of which contain a projection screen to create a visual, musical experience. Brass strings will be attached along the roof of the Des Moines Civic Center, stretched over Third Street, and down to the harp in Cowles Commons.

“I’m going to be setting up a stage and then we’re going to run the strings all the way across the street and to the top of the Des Moines Civic Center,” Brook says. “So it’s going to be a fairly large installation. Some of the strings will be as much as 200 feet long and so I think it’s going to be really spectacular.”

For next week’s performances, Brook will be accompanied by a pianist, a violinist and a drummer for all-original music, which she calls “evocative.” “We will do a variety of different things,” Brook says. “There will be solo songs so you get to just experience the harp. There will be pieces where it’s just the pianist and I, or just the violinist and I, and we will have big, full, high-energy full band pieces.”

Seven one-hour performances are scheduled over three days — and all are free. Catch Sonic Butterfly on Thursday, September 15th at 6:30 p.m.; Friday, September 16th at 12 p.m., 3 p.m. and 6:30 p.m.; and on Saturday, September 17th at 10 a.m., 12 p.m. and 3 p.m.