[citation needed] In his role as the society's sole artistic director, he brought to London Marilyn Horne, Joan Sutherland, and Boris Christoff.
He was also responsible for introducing Sherrill Milnes, Ruggero Raimondi, and Montserrat Caballé.
He was a highly regarded expert in the field of opera with an extensive knowledge of the history of vocal music, and his books include volumes 1 and 2 of The Record of Singing and The Great Caruso.
[3] In the review of this book for Opera News, Albert Innaurato writes, "His is the only biography to understand how Callas compares with and differs from Tetrazzini, Ponselle and Patti.
In fact his crisp, unsentimental manner may unsettle some readers—he responds to Callas as an artist, not as a tragedy queen, and does not linger over her miserable last years or indulge in psychologizing.