He then became an original member of Ballet Society, formed by Balanchine and Lincoln Kirstein in 1947, and later of its successor, the New York City Ballet. During the four decades that he spent in these companies, he created a number of important roles and participated in many historic performances. At the first performance of the New York City Ballet on October 11, 1948, he danced in all three ballets on the program: "Concerto Barocco, Orpheus", and "Symphony in C". Decades later, during the troupe's 20th anniversary season he appeared in the premier of Jacques d'Amboise's "Tchaikovsky Suite No. 2" in collaboration with Robert Irving and John Serry Sr.. This is a selected list. Choreography is by George Balanchine unless otherwise noted. Principal source of information is The Balanchine Catalogue. Early in his career, it became clear that Moncion would never be a true "danseur noble". He lacked the elegance of bearing and refinement required for princely roles. Yet it was equally clear that he was capable of effective portrayals in many different roles as a "premier danseur". He was a dashing figure in the Balanchine dances for the Broadway production of "The Chocolate Soldier" (1947), swirling and twirling with Mary Ellen Moylan. He was a delicately tender partner to Tanaquil Le Clercq in Jerome Robbins's meditative "Afternoon of a Faun" (1953), bringing a sensual, feline languor to the part. He was dramatically powerful in the title role of Balanchine's "Prodigal Son", entranced by the Siren of Yvonne Mounsey and then heartbreakingly contrite as he painfully made his way home to his father. In stark contrast, he was hilariously funny as The Husband in Robbins's "The Concert", smoking his cigar and flitting about the stage to butterfly music. And, of course, he was mysteriously compelling and beautiful in "Orpheus", as the brooding Dark Angel, the role for which he is perhaps best remembered. In the 1950s and 1960s, Moncion experimented with choreographing works of his own. He made four for the New York City Ballet and two for other companies. Moncion's surname is well known in the Dominican Republic, as his family is connected to General Benito Monción (1826–1898), an army officer of French descent who fought in the Dominican Restoration War.