This weekend, a musical composition about the Schuylkill and Delaware Rivers will premiere in Philadelphia, evoking both the movement of their currents, and their economic ebb and flow.

"RIVERS," for prepared piano and prepared cello, was written to accompany dancers and a projected film. While the Brooks-Delaney Duo (Bethany Brooks and Daniel Delaney) perform, three dancers will perform manipulations on the strings of the instruments, choreographed by Lea Fulton. The instruments are not prepared in advance of the show, but during.

"The idea came about because of the amount of work beforehand," said composer Josh Stamper, noting it can take a few hours to prepare a piano with chopsticks, paper clips, coins, little pieces of rock, and anything else from the John Cage songbook. "I'm trying to make it as practical as possible."

Stamper is at work on a series of compositions focused on the four elements -- earth, wind, fire, and water -- and how those are present in Philadelphia. "RIVERS" is the first.

"For as long as I can remember, the movement of air, the movement of water, the movement of fire -- any natural movement like that has been incredibly compelling to me," said Stamper in his Collingswood, New Jersey, home. "The dynamism off the currents going on at the same time and different rates, the way those currents are constantly adjusting to things obstructing their path -- even microcurrents responding to a fishing lure dropped into the water -- is interesting to me."

The shimmery sounds of strings manipulated by foreign objects -- at one point, a dancer rakes a braided fishing line through the piano strings -- ripple on top of the piano and cello duet, like light on water. This piece, however, is not just water-meeting-water harmonies.

One of the major obstructions to Philadelphia's rivers is Philadelphia itself, a city of industry that has been exploiting both rivers for centuries.

The relationship between Philadelphia and its waterways brings the tension in the third movement of the work.

"Rivers were a conduit for transporting industry. They representing a flourishing," said Stamper. "You have that simultaneously beautiful thing -- a symbol of flourishing -- and the scarring that happens."

The dance and music are designed to work in concert with the third element of the evening Saturday at 8 p.m. at the Trinity Center for Urban Life near Rittenhouse Square: a film of poetic imagery and dance by Ben Stamper, the brother of the composer.