Altarpiece two, three, and multiple panels respectively. In the thirteenth century each panel was usually surmounted with a pinnacle, but during the Renaissance, single panel, or "pala", altarpieces became the norm. In both cases the supporting plinth, or "predella" often featured supplementary and related paintings. If the altar stands free in the choir, both sides of the altarpiece can be covered with painting. The screen, retable or reredos are commonly decorated. Groups of statuary can also be placed "on" an altar. A single church can furthermore house several altarpieces on side-altars in chapels. Sometimes the altarpiece is set on the altar
Saint Peter Martyr Altarpiece testimony) also mention a second altarpiece by the artist in the same church, also dating to 1476, now known as the "Saint Peter Martyr Altarpiece"'. It is therefore theorised that the altarpieces were both dismantled during rebuilding of the church in 1776, then sold to the antiquarian Grossi who sold all the panels separately and grouped some of them into the altarpiece that Cardinal Zelada bought from him. Federico Zeri and Rodolfo Pallucchini then joined the altarpieces together, initially referring to the first (the high altarpiece), the "Pietà" in the Metropolitan Museum, and then to the "Madonna" in the Museum