I learned from a video about this painting [4 min 34 sec] that underneath the fiddler is probably another self-portrait. The clothing in this is too unsuitable for her to wear while painting, so I think it would have been neat if the painting within the painting was of her wearing what she'd normally have on while painting. Something like the reverse of what Norman Rockwell created with his "Triple Self-Portrait."
Wikipedia entry on Judith Leyster: https://en.wikipedia.org/wiki/Judith_Leyster
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Added on November 29, 2018. This is a closer view, taken where the painting is usually hung with the other Dutch paintings on wood wall panneling. I think the colors in this picture are closer to what I see in person.
