The Canticle of Miriam
This painting pictures Exodus 15:20-21, "So Mary the prophetess, the sister of Aaron, took a timbrel in her hand: and all the women went forth after her with timbrels and with dances: And she began the song to them, saying: Let us sing to the Lord, for he is gloriously magnified, the horse and his rider he hath thrown into the sea."
As specified in the passage, Miriam holds a timbrel in her left hand. The woman behind her echoes her dancing gesture while the one on the far left repeats the timbrel. Other figures play various instruments while a mother suckles her child in the foreground.
The man in red could be Aaron.
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Read more about Miriam.
Photographed at the cathedral by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.