Lisa, alone with her sax...and Maggie's bow.
Here's the story: Ever since Maggie was about 8, she felt that Lisa was a 'shadow'. A shadow so overbearing, Maggie felt that no matter how hard she tried, no one would take her seriously because of how gifted Lisa is.
So, in one anger filled rant where Lisa tried to make peace with her little sister, Maggie told Lisa to "Back off!", removed her bow and threw it in Lisa's face. Saddened her sister is bitter with resentment towards her, Lisa tied Maggie's bow to her saxaphone...keeping it close so one day when Maggie isn't so spiteful towards her, she can give it back.