What was plain was that during those years, her family, formerly middle class, knew great hardship. Long afterward, when she was safely swathed in the jewels and furs that are a diva’s prerogative, Ms. Caballé recalled a time when she owned only a single dress. To the sneers of her classmates, she wore it to school every day for a year.

Her parents, Carles Caballé i Borrás and Anna Folch, loved music and, listening to their collection of opera records, young Montserrat was smitten. At 8, she took it upon herself to learn “Un Bel Di,” Cio-Cio-San’s aria from Puccini’s “Madama Butterfly,” and so she did, by ear, singing it for her family.

It was clear that the child had a remarkable talent. Though her parents could scarcely afford it, she soon began studies at the Conservatori Superior de Música del Liceu in Barcelona, first on the piano and then, as a young teenager, in voice.

Her primary voice teacher, Eugenia Kemeny, made her pupils spend a full year doing vocal exercises and breath training before they could approach real music. That training, Ms. Caballé would say afterward, let her sustain her career as long as she did.

When Montserrat was about 16, her father fell ill and could not support the family, forcing her to withdraw from the conservatory. She worked for nearly a year in a handkerchief factory before attracting the sponsorship of wealthy Barcelona patrons, who agreed to support Montserrat and her family. In gratitude, she returned annually throughout her career to sing in Barcelona.

At 20, Ms. Caballé graduated from the conservatory with its gold medal for voice and embarked on auditions with Italian opera companies. Nervous and untried, she failed at all of them, inspiring one agent, she recalled, to suggest she forsake singing and find a husband.

Trying her luck in Switzerland, she caught on with the Basel Opera in 1956, singing small roles until she was called upon to sing Mimì in place of an ailing soprano. She spent the rest of the ’50s and early ’60s singing throughout Europe.