The musician credited with transforming jazz music in the 20th century is Louis Armstrong. His innovative approach to trumpet playing and vocal improvisation significantly influenced jazz as a genre. Armstrong popularized the concept of solo performance, moving beyond collective playing to spotlight individual talent. His unique style, characterized by a distinctive timbre and rhythmic flexibility, helped redefine the genre and paved the way for future jazz artists. Armstrong's contributions not only shaped jazz but also had a profound impact on popular music as a whole.