Gaspar Cassadó was born in Barcelona on September 30, 1897, into a musical family. His father, Joaquin, was a composer and church musician, and ran a piano store with his wife, Agustina Moreu. Gaspar began his musical training at the age of five, singing in the church chorus conducted by his father. He also began cello studies with Dionisio March, and his talent was quickly apparent. At the same time, Gaspar's older brother, Agustin, was demonstrating great promise as a violinist. Joaquin Cassadó was determined to give his sons the best musical training possible, and in 1907 he moved the family to Paris, where they remained for seven years. With the help of a grant from the city of Barcelona, Agustin took lessons from the great French violinist Jacques Thibaud, while Gaspar began studying with the man who would become one of the central figures in his life, fellow Catalonian Pablo Casals.