We have nothing from Berlioz as memorable as Mozart’s sartorial metaphor. The French composer recognized, no less than other opera composers, that singers were vital to the success of his vocal works. There is no reason to suppose that Berlioz looked on singers, or could afford to look on them, as mere adjuncts to his compositional plans, whose abilities, less open to new technical demands than instrumentalists’, could be bent to his creative will. Indeed, singers may be counted among his friends as well as among the objects of his bile and the butts of his humor. Berlioz is even one of the select group of composers who married singers, including Hasse, Mozart, Rossini, Johann Strauss the younger, Verdi, and Richard Strauss.

Although Berlioz’s works, unlike Mozart’s and Verdi’s, were rarely first performed by pre-selected singers, the matter of suiting the voice to the role concerned him closely: “The art of writing for individual voices is in fact conditioned by a thousand different factors which are hard to define but which must always be borne in mind; they vary with the individual singer.” This section of the Traité d’instrumentation is necessarily concerned with voice-types, as it deals with choral rather than solo voices. But when a composer writes for a particular singer, he attends not to the vocal category but to that individual’s qualities at that time in her career. Over the years, as her voice changes, the same singer may perform roles assigned to different voice-types. Furthermore leading singers in a revival are allocated principal roles conceived for someone else. In these circumstances, roles have often been modified. In the nineteenth century this led less to the composition of new arias (as earlier happened in Handel and Mozart) and more to transposition, adjustment, and alterations of detail. This is not necessarily a harmful practice, and it continues to the present day, despite establishment of a canon and the still powerful concept of Werktreue, or fidelity to the text. By his own account Berlioz as a young operagoer was an obstreperous adherent of such fidelity, pillorying performers and arrangers who departed from the sacred texts of Gluck, Beethoven, and Weber.