This thesis is based on the conviction that the greatest musical performers of history can and should be granted the same level of academic scrutiny and study as is so often received by the greatest composers. Composers had the early advantage of producing durable manuscripts, while performers prior to the age of recording were unable to leave more than impressions in the minds of those who heard them. With the recent successes of numerous investigations into performance and recordings, including the CHARM and CMPCP projects, such studies are becoming ever more viable and significant. The thesis focuses on the violinist Jascha Heifetz (1901-1987) and primarily his performances of the Bach solo violin works (BWV 1001-1006). While there have been studies of individual pieces, of particular performers, and of multiple recordings of the same piece, a study focussing on specific repertoire played by a specific performer is something that has been somewhat overlooked in the literature. The thesis draws on numerous methods to distil what is distinctive and unique about Heifetz. This includes an examination of what and how the performer played, why the performer played that way, and how that way of playing compares to other performers. The study concludes with a discussion of Heifetz’s unique performer profile in the context of violin performance history. Focussing on one of the most famous and successful performing musicians of the twentieth century along with some of the most frequently played pieces, this case study will suggest research methods and approaches transferable to related studies. The thesis draws on original interviews with former Heifetz students, friends, and colleagues, and on over thirteen months of archival research in the Jascha Heifetz Collection held by the Library of Congress. This array of previously untapped material aided the analytical and empirical investigations into Heifetz’s uniqueness.