In his symphony “Il maníatico” (1780), Gaetano Brunetti gave a musical portrayal of monomania decades before it became a staple of nineteenth-century alienism (psychiatry), as well as of Romantic music and art. A detailed analysis of his symphony shows both the presenting features of what he called manía as well as the stages of the “maniac's” interaction with the surrounding “normal” world. These stages respond to widely known mental peculiarities of several generations of Spanish royalty, whom Brunetti served as court composer. Though its court audience would likely have compared this portrayal of obsession to Cervantes's Don Quixote, Brunetti's symphony may also have sent a coded message of sympathy to his patron, the crown prince who would later reign as Carlos IV and who struggled with his obsessional father, then reigning as Carlos III. At the same time, Brunetti mocked Luigi Boccherini, his rival as court composer. By presenting a subversive reimagining of the “normal” symphonic world, Brunetti characterized the mannerisms of classical style as monomania writ large. In the following decades, the term fixe Idee emerged in German literature and usage considerably before the French idée fixe. Both concepts emerged from literary, rather than medical, sources. Though Don Quixote remained a touchstone for reflections on “madness,” Brunetti's symphony anatomized obsession decades before medical discourse gave its clinical description.