Vatican City: Euphrasian Basilica

Vatican City issued this set of three stamps (Scott 960-962) in 1994 to mark the 13th International Convention of Christian Archeology, which was held in Split, Croatia. The images on the stamps are details from the Euphrasian Basilica in Porec, Croatia. The mosaics depicted are located in the east-end apse of the basilica, and are indeed quite dramatic. The 700 lira stamp shows Bishop Euphrasius, Archdeacon Claudius, and Claudius' son; the 1500 lira stamp shows the Madonna and Child with two angels; the 3000 lira stamp shows Christ and the Apostles Peter and Paul. In addition to the persons on the stamps, the overall mosaic includes all twelve of the disciples of Jesus, plus numerous saints. When this set was recommended to me, I inquired as to the organ "tie-in." I was told that while an organ is not present on any of these stamps, there is an organ visible elsewhere in the mosaic. I have searched for a couple of years now and have yet to find any hint of an instrument, nor pipes, nor even anything like a pan-flute within the mosaic. I am including this post for the sake of completeness, but I am not convinced that there are any pipes, let alone an entire instrument, present in the mosaic. I will be happy to be corrected by anyone who knows better. I have included a couple of detailed photographs of the mosaic for any who wish to explore and seek to discern a pipe or two! I do note that Euphrasius is holding a church building, which may be a representation of the basilica; within the basilica there may be an organ (I have not found information about one yet), and by extension the Bishop is holding a representation of an organ?