John Philip Sousa is best known for composing which type of musical ensemble?

John Philip Sousa is best known for composing for the brass band, which is a type of ensemble characterized by the use of brass instruments, percussion, and sometimes woodwinds. Sousa's extensive catalog of music includes numerous marches, which were particularly popular in the late 19th and early 20th centuries. His most famous work, "The Stars and Stripes Forever," is a march that has become synonymous with American patriotism and the brass band tradition. Sousa's compositions were designed to be performed by large ensembles, typically featuring brass instruments prominently, reflecting his expertise and dedication to this musical form.

In contrast, the other options represent different musical genres and ensembles not primarily associated with Sousa's contributions. Barbershop quartets focus on vocal harmonies, dance orchestras emphasize rhythm and popular dance music, and jazz ensembles explore improvisation and swing, none of which align with Sousa's primary body of work.