There are many allusions in "In Memory of Radio," which are looked into more closely in the "Characters" and "Glossary" sections. Allusion in this poem can be understood as the speaker's various brief mentions of historical pop culture and literary elements.
Stanza I: The poem opens with an allusion to Lamont Cranston/The Shadow, a superhero that fights crime by clouding up other people's minds. There is also an allusion to Jack Kerouac, a Beat novelist and friend of Baraka's in the 1950s. Kate Smith in Stanza I was a popular singer of the mid-twentieth century. WCBS is an allusion to CBS New York, a TV show that has been popular since the 1930s.
Stanza III: "Mandrake" is an allusion to the superhero Mandrake the Magician, a superhero who fought crime by making hypnotic gestures and controlling men's minds. Oral Roberts was a Christian televangelist; F.J. Sheen was also a televangelist and a bishop of the Catholic church. Hitler was the leader of Nazi Germany during WWII who was responsible for the Holocaust and countless human deaths. Goody Knight was a conservative governor in California during the 1950s.
Stanza V: "The Red Lantern & his undersea folk": the Red Lantern Corps were the anti-heroes of the DC comics universe. They are driven by the power of rage; a rage that perhaps was tapping into the rage felt by minority groups throughout the 20th century. "Let's Pretend" was a radio show for children that focused on trying to foster their imaginations.