A German tragedy on a Spanish subject transformed by an Italian composer into an opera with a French libretto - which was later translated into Italian. This is a particular and original example of literary and musical evolution in the geographic frame of Romantic Europe. After studying how the structure changed, going from Don Carlos to Don Carlo, in order to fit the transformation of the theatre piece into French opera, the author proposes to analyse some selected examples, musical consequences of linguistic vicissitudes, going from the original composition to the final Italian translation.