Kirkman left the band The Men in 1964 to become a founding member and sometime leader of the musical group the Association. Kirkman co-wrote some material with fellow group member and friend Jules Alexander. His "Requiem for the Masses," a song written about the war in Vietnam, featured requiem-style vocals. In 1964, while he was dating a girl named Barbara Bivens, he introduced her sister Beverly to what became, with her as their lead singer, the folk rock group We Five.