Anaphora, a loose local ensemble that doubles as a presenter and promoter of contemporary classical music, has a promising program lined up for its concert at the Green Mill on Sunday; in addition to performances of pieces by Arvo Part and Sarah Ritch, there will be a world premiere of string quartet by Sam Krahn that Anaphora commissioned and two pieces by sorely underrated Chicago composer George Flynn, one of which he’ll play himself on solo piano. It’s at 2 PM, and cover is $5–a very good deal for music that’s very much worth hearing.