In 1923 and thanks to the friendship with Francesco von Mendelssohn he met the singer and pianist Giulietta Gordigiani,[3] with whom he lived for more than three decades, settling in Florence.

Gaspar and Giulietta created a cello and piano duo with which they toured the European stages for more than a decade, achieving great success.

Giulietta Gordigiani, widow of Robert von Mendelssohn, offered him fundamental support for the development and promotion of his career, as well as an excellent piano collaboration.

His career suffered a very significant and irreparable decline in the postwar period, due mainly to a famous letter published by his former teacher Casals in the New York Times accusing him of collaboration with the fascist regimes and asking that Cassadó not be allowed to play in the allied countries.

[8] On the invitation of his great friend Alicia de Larrocha, with whom he had a cello-piano duo (touring extensively with him from 1956–58), Gaspar Cassadó played concerts and led frequent classes at Academia Marshall in Barcelona.