Oil transferred from panel to canvas, 220 x 136 cm
Pinacoteca Nazionale, Bologna
At left are St. Paul (with the sword, emblem of his martyrdom) and St. John the Evangelist (before whom note the eagle, his attribute, standing on a book). At right are St. Peter (crozier, head balding from the back) and St. Mary Magdalene (holding an ointment vessel).
Angels singing in Heaven from a shared songbook were a common device in this century. See this page for more examples.
Read more about images of St. Cecilia.
Read more about images of St. John the Evangelist.
Read more about images of St. Mary Magdalene.
Read more about images of St. Paul.
Read more about images of St. Peter.
Source: Paul Hermans via this page at Wikimedia Commons.