Castel had over 200 operatic roles in his repertoire. His singing career took him around the world to work with such companies as Palacio de Bellas Artes, Mexico City; Finnish National Opera, Helsinki; New Israeli Opera, Tel Aviv; Opera Metropolitana, Caracas; Teatro Nacional de São Carlos, Lisbon; Spoleto Festival, Spoleto, Italy; Maggio Musicale Fiorentino, Florence; Semper Oper, Dresden; and in the United States, the Opera Company of Philadelphia, Seattle Opera, San Francisco Opera, Chicago Lyric Opera, Ravinia Festival, San Antonio Grand Opera Festival, New Orleans Opera, Baltimore Opera, Miami Opera, Santa Fe Opera, Central City Opera, and St. Louis Opera, among others. On the concert stage, he often included Jewish music in his programs, and he served as a cantor at Scarsdale Synagogue in Westchester County, New York, and Progressive Synagogue in Brooklyn, New York. The New York Times commented: "Reviewers over the years praised Mr. Castel’s rich dramatic characterizations, his sensitive musicianship and, not surprisingly, his impeccable diction."
