Wacky public art project that tunes all the guard rails along a parkside or path to real notes. Must be somewhat muffled to keep the neighbors happy. Brass markers in the cement show you what notes are which and even give you songs to play. Would be a fun companion to the brass dance steps on Capitol Hill in Seattle.
Alternate version: Wooden fenceposts tuned like a marimba would do the same thing and sound better. Should be tuned funky, like in pentatonic scale or all minor scales.