Composer and instrument builder Paul Rudolph makes music from garbage. He combs recycling centers and scrap yards for what he calls "found object instruments" -- propane tanks, film reels, artillery shells and other items that he likes the sound of.  Rudolph sometimes modifies the objects and then uses the newly-minted percussive instruments in his music performance group GLANK,  which has appeared at the Eagle Rock Music Festival in Los Angeles and Maker Faire in New York City. John Powell, physicist and author of How Music Works, chimes in on the physics of making music.