In folktales of this kind, the mother (and father) figures are split into two characters, one good, one evil. Here the “bad breast,” the stepmother who feeds him leftovers and sets her husband the task of killing him, is contrasted with “the good breast” of the seven cows that give him milk and protection.
The motif of the flutes of joy and of sorrow (B 501.1) has a surprising development here. The hero, being left only with the flute of joy, can express and communicate no sorrow. All his feelings come out sounding happy on the flute of joy. It reminds one of the passage in Kierkegaard on the way the artist is fated to turn suffering into notes of music.
[AT 534, The Youth Who Tends the Buffalo Herd (IO).]