The study of interpretation is paramount for any performing artist. Given that the bulk of classical music is connected to a sophisticated notation-based tradition, the marked-up score can possibly inform and connect us, with remarkable precision, to the legacy of a past master-interpreter. Manuscripts with performer's markings, the personal performing scores of the artist, the teaching materials the artist used in guiding students, personal cadenzas, and the adaptations and alterations made by students and disciples, are all materials that can show traces of the journey and struggle of the interpreter. The thought process that may be revealed from these materials can help us understand the aesthetic and technical preferences and priorities of an artist. In connection with Eugène Ysaÿe, the immensely influential Belgian violinist, who dominated and revolutionized violin playing at the turn of the twentieth century, an exemplary resource for studying marked-up violin scores exists at the Juilliard School: the materials that belonged to two of his favored, and successful, American students, Louis Persinger and Viola Mitchell. For the performer-scholar, the Louis Persinger Collection and Viola Mitchell Collection provide a remarkably clear view into the aesthetic and mindset of Persinger, Mitchell, and Eugène Ysaÿe.