When Rossini died some 140 years ago, Verdi decided that the least he could do for his hero was to write a requiem for him. He talked it over with other composers, and they decided to co-author it, to co-compose it. They finished the job, but Verdi was so dissatisfied with the result that he refused to allow it to be performed in his lifetime. It was not performed until about 100 years after his death—in Manhattan. That is the story of many attempts at co-authorship. Peter Costello is no Verdi or Rossini. Nor am I! But you still may…