The square antechamber has a vault in the form of a truncated pyramid with four lunettes, three containing windows and one the arch into the baptistry proper. The central panel is by Il Passignano, and features a band of five angels on vocals, organ, lute, violin and flute with others in attendance. A pair of putti hold up the music that they are playing, which is an antiphon in honor of the Immaculate Conception.