an·tiph·o·nal 
(ăn-tĭfə-nəl)
(ăn-tĭfə-nəl)adj.
1. Relating to or resembling an antiphon.
2. Answering responsively, as in antiphony.
3. Occurring or responding in turns; alternating: "a couple of comedians ... perfecting their antiphonal patter" (P.D. James).
n.
An antiphonary.
an·tipho·nal·ly adv.