A tribute to the composer on his 100th birthday: We listen in on a 1942 John Cage radio play, "The City Wears a Slouch Hat." We have a vox-pop asking "Who's John Cage?"; an audio illustration by Jay Allison of a "John Cage and Merce Cunningham" collaboration; an excerpt from the film "John Cage: Ecoute (Listen)"; and, from the series Echoes, "Thoughts in Sound: John Cage- Imaginary Landscapes." Laurie Anderson and Ken Nordine offer homages to the composer. And we hear Cage's "In a Landscape," Suite for Toy Piano, and "Variations IV."