In January 1921, Respighi and Elsa began their first tour as joint performers, marking Elsa's debut as a performing concert artist. They were joined by violinist Mario Corti. The tour saw dates across Italy, followed by Prague, Brno, and Vienna. The time away from his teaching duties at the Liceo Musicale in Rome led to his employers issuing a letter suggesting he return to fulfil them for the remaining months of the academic year. By 1921, Respighi had begun a lifelong friendship with the writer and journalist Claudio Guastalla, who encouraged him to compose a new opera and offered to write its libretto. This created a spell of productivity and Respighi eagerly completed "Belfagor", his first opera in a decade, without the spells of depression that had usually affected him once he had finished a work. Guastalla would exclusively write the libretto for all of Respighi's future operas, and influence the conception or programmes for some of his non-operatic compositions.