Louis Armstrong was an American trumpeter, singer and bandleader widely regarded as one of the founding figures of modern jazz. Active from the 1920s onward, he profoundly transformed the role of the soloist through his powerful trumpet playing, sense of swing and innovative approach to improvisation, while also popularizing scat singing and a uniquely recognizable vocal style. With songs such as West End Blues, What a Wonderful World and When the Saints Go Marching In, Louis Armstrong played a major role in bringing jazz to audiences around the world.