In the summer of 1951, Corelli won the Maggio Musicale Fiorentino in Florence, earning a debut at Spoleto the following fall. He was originally scheduled to sing Radames in Verdi's Aïda and spent three months preparing the role with conductor Giuseppe Bertelli. However, Corelli eventually switched to Don José in Bizet's Carmen, feeling that at this point he lacked the technical finesse and legato for the role of Radamès. In November 1951, he made his debut at the Rome Opera as Manrico in Il trovatore opposite Maria Caniglia as Leonora. The next year he appeared in operas with smaller opera houses throughout Italy and on the Italian radio. In 1953 he joined the Rome Opera's roster of principal tenors where he spent much of his time performing through 1958. His first role with the company in 1953 was that of Romeo in Zandonai's rarely heard opera Giulietta e Romeo. Later that season he sang Pollione in Bellini's Norma opposite Maria Callas in the title role. It was the first time the two sang opposite one another and Callas immediately became an admirer of Corelli. The two performed frequently with each other over the next several years in a partnership that lasted to the end of Callas's career.
While singing at the Rome Opera, Corelli also made numerous appearances with other opera houses both in Italy and internationally. He made his first appearance at La Scala in Milan in 1954, as Licinio in Spontini's La vestale opposite Callas's Giulia for the opening of the 1954-1955 season. He returned several more times to that house over the next five years, singing opposite Callas in productions of Fedora (1956), Il pirata (1958) and Poliuto (1960). He also notably portrayed the role of Dick Johnson in a highly celebrated performance of La fanciulla del West at La Scala in 1956, opposite Gigliola Frazzoni and Tito Gobbi, which was broadcast live on Italian radio. Other important debuts for Corelli soon followed, including his first appearances at: the Maggio Musicale Fiorentino in Florence and the Arena di Verona Festival in 1955; the Vienna State Opera, as Radamès, and the Royal Opera House, Covent Garden, in London, as Cavaradossi, in 1957; the Teatro Nacional de São Carlos in Lisbon, the Lyric Opera of Chicago and the San Francisco Opera in 1958; and the Berlin State Opera in 1961. Among the many triumphs of the decade for Corelli were two highly celebrated performances at the Teatro di San Carlo in Naples, a 1958 appearance as Don Alvaro in La forza del destino opposite Renata Tebaldi as Leonora and a 1959 performance of Maurizio in Adriana Lecouvreur opposite Magda Olivero in the title role.
During his early career, Corelli sang in a number of rare operas in which he triumphed including performances of Spontini's Agnese di Hohenstaufen, Handel's Giulio Cesare and Hercules, Prokofiev's War and Peace, and the world premiere of Guido Guerrini's Enea. By 1960 his active repertory included some 30 roles including the title role in Giordano's Andrea Chénier, Turiddu in Mascagni's Cavalleria rusticana, Rodolfo in Puccini's La bohème, and the title roles in Verdi's Don Carlo and Ernani.
In 1957 Corelli met soprano Loretta di Lelio when she came backstage after one of his performances at the Rome Opera House to get his autograph. They began seeing each other romantically and married in 1958. After their marriage, Loretta gave up her fledgling opera career to serve as her husband's business manager, secretary, public relations agent, cook, and English translator. Their marriage ended upon Corelli's death forty-five years later. (Wikipedia)