Emmanuel Church of Boston’s “Late Night at Emmanuel” series presents a cabaret-style concert, including the performance of A Supermarket in California by Elena Ruehr. Written for baritone and string quartet, text author Allen Ginsberg bases the words on thoughts by Walt Whitman. The poem describes an imaginary encounter between the poet and Walt Whitman, whom Ginsberg greatly admired, as Whitman wanders around a supermarket, then out into the night, and finally to the Greek underworld. The work, written in 2016, will be performed by the commissioning artists: David Kravitz, baritone, and the Arneis Quartet. The concert takes place September 23.