Though adored by many opera enthusiasts, Callas was a controversial artist. While Callas was the great singer often dismissed simply as an actress she considered herself foremost a musician, that is, the first instrument of the orchestra." Grace Bumbry has stated, "If I followed the musical score when she was singing, I would see every tempo marking, every dynamic marking, everything being adhered to, and at the same time, it was not antiseptic; it was something that was very beautiful and moving." Victor de Sabata confided to Walter Legge , "If the public could understand, as we do, how deeply and utterly musical Callas is, they would be stunned", and Serafin assessed Callas's musicality as "extraordinary, almost frightening." Callas possessed an innate architectural sense of line-proportion and an uncanny feel for timing and for what one of her colleagues described as "a sense of the rhythm within the rhythm".