Denver-based artist Jim Green doesn't make work you can hang on the wall or place on a pedestal. In fact, it's quite invisible. But if you've ever had a sink sing to you at the Denver Art Museum or heard the phantom subway train near the 16th Street Mall, you've encountered his creations. Green has a new installation at the Museum of Contemporary Art using whoopie cushions. KCFR's Megan Verlee has this profile.