One of the major questions that will go forever unanswered is "How did jazz start?" The first jazz recording was in 1917 but the music existed in at least primitive forms for 20 years before that. Influenced by classical music, marches, spirituals, work songs, ragtime, blues and the popular music of the period, jazz was already a distinctive form of music by the time it was first documented.
The chances are that the earliest jazz was played by unschooled musicians in New Orleans marching bands. Music was a major part of life in New Orleans from at least the 1890's with brass bands hired t…