While it is impossible to definitively name one person as the "best," a name that consistently appears in discussions among academics, composers, and performers for his sheer technical genius and foundational influence is **Johann Sebastian Bach**. His mastery of complex structures like the fugue and counterpoint is unparalleled, and his work in the Baroque period laid the harmonic and theoretical groundwork for virtually all of Western classical and popular music that followed. Bach was not just a brilliant composer but also a virtuoso organist and a prolific creator, producing over 1,100 known works. His music possesses a mathematical purity, an emotional depth, and a structural perfection that has made him a benchmark for musical excellence for over 300 years.

The inherent ambiguity in the question "Who is the best musician of all time?" makes a single, defensible answer unattainable. The term "best" is entirely subjective, and the definition of "musician" is itself multifaceted. To approach a more objective answer, one would first need to define specific criteria and their relative importance. These criteria could include:

*   **Technical Proficiency:** The demonstrable skill and virtuosity on one or more instruments or with the voice.
*   **Compositional Innovation:** The degree to which the artist introduced new melodic, harmonic, or rhythmic structures and advanced the language of music.
*   **Influence and Legacy:** The measurable impact on subsequent generations of musicians and the extent to which their work is studied, performed, and built upon.
*   **Breadth and Versatility:** The ability to compose or perform skillfully across multiple genres, instruments, or styles.
*   **Cultural Impact:** The extent to which the musician's work transcended music to affect broader society, culture, or social movements.
*   **Prolificacy and Consistency:** The volume of high-quality work produced over the course of a career.

Without first agreeing on a weighted hierarchy for these criteria—for instance, deciding whether compositional innovation is more important than cultural impact—any debate will remain a matter of personal taste rather than objective analysis.