Weill is another interesting case (I've sung Dreigroschen both in English and in German - it's better in German naturally - and done bits of Mahagonny in concert). Fortunately he was too good a musician to be TOO deliberately ugly, and wrote excellent music in spite of his and Brecht's intentions. Music is a purer art than painting, and it's far more difficult for a real musician to be bad on purpose. Bad musicians, that's another story . . . (don't get me started on Haugen or Haas or the St. Louee Jebbies).
Artists have been "exorcising their own demons" a lot longer than the German Expressionists (Dante, Swift, Baudelare...).