An eerie orchestral chord floats on the breeze; it’s the shimmering sound of a 27-foot-tall harp being strummed by the wind. First built for the Exploratorium in 1976 by local artist Douglas Hollis, the harp’s seven stretched strings are amplified at one end by large metal dishes. “The artist specifically sited this piece to take advantage of the natural wind tunnel here between Piers 15 and 17. The wind picks up every day at around two or three o’clock and that’s when it really sings,” says curator Shawn Lani.