### My Answer to the Question
In my opinion, the best musician of all time is Ludwig van Beethoven. His profound impact on classical music, through compositions like the Ninth Symphony and Moonlight Sonata, revolutionized the art form by bridging the Classical and Romantic eras. Beethoven's ability to innovate despite personal hardships, such as his progressive deafness, showcases unmatched creativity and resilience. His work has influenced countless genres beyond classical, from rock to film scores, making him a timeless figure whose legacy endures across centuries.

### Analysis of the Prompt's Ambiguity and Suggestions for Objective Criteria
The original prompt—"Who is the best musician of all time?"—is inherently ambiguous because terms like "best" and "musician" are highly subjective and lack clear definitions, leading to answers shaped by personal taste, cultural bias, or anecdotal evidence rather than empirical standards. "Best" could interpreted in myriad ways, such as technical proficiency, commercial success, emotional resonance, or innovation, while "musician" might encompass composers, performers, instrumentalists, singers, or producers across diverse genres like jazz, hip-hop, or folk, and "of all time" spans global history without accounting for era-specific contexts or accessibility of records from ancient times. This vagueness invites endless debate without resolution, as seen in how one might favor Bob Dylan for lyrical depth while another prefers Mariah Carey for vocal range. To make the question more defensible and less subjective, specific objective criteria would need to be defined, such as: (1) quantifiable metrics like total record sales or streaming numbers (e.g., exceeding 1 billion units sold); (2) awards and recognitions, such as the number of Grammy or equivalent international accolades; (3) cultural impact measured by citations in academic studies, covers by other artists, or inclusion in global "greatest" lists (e.g., Rolling Stone's rankings); (4) longevity and influence, quantified by the number of years their work has remained in charts or inspired derivative genres; and (5) technical benchmarks, like vocal range in octaves or compositional complexity via music theory analysis. Additionally, narrowing the scope—e.g., to a specific genre (rock), era (post-1950), or type (solo instrumentalist)—would further reduce subjectivity by creating a bounded framework for comparison.