Period polynomials and Ihara brackets
  Schneps [J. Lie Theory 16 (2006), 19--37] has found surprising links between Ihara brackets and even period polynomials. These results can be recovered and generalized by considering some identities relating Ihara brackets and classical Lie brackets. The period polynomials generated by this method are found to be essentially the Kohnen-Zagier polynomials. 
Jean-Gabriel Luque, Jean-Christophe Novelli, and Jean-Yves Thibon