After early study with his father, composer and organist Joaquin Cassadó, Gaspar attended the Barcelona Conservatory and also took lessons from Casals. He enjoyed an international career, playing with such greats as Bauer, Rubenstein and Menuhin.
He was known as a refined player with beautiful tone and strong technique. Cassadó composed several concertos and much chamber music. His work was influenced by Falla and Ravel.