At his prime, Mustafà possessed a voice of superior strength and beauty, and he mastered the trills and coloraturas to the utmost perfection.

Being a man of great honour and responsibility, he was eventually nominated as a possible candidate, and finally elected, for the post of "Direttore Perpetuo" of the Sistine Chapel in 1878.

However, the whole idea was abandoned shortly afterwards due to a role confusion—the emasculated Klingsor was not a castrato, but a eunuch castrated past puberty and thus singing baritone, not soprano.

In person Mustafà was tall and broad, rather plump, very stylish and charismatic in countenance—in older age, he always wore glasses due to his failing sight.

[4] Mustafà's role as a director in the Sistine Chapel is considered to be of great importance, and a book about his life was written by Alberto de Angelis and released in 1926.