1) American bandmaster 2) Author of The Fifth String 3) Authority on the march 4) Band man 5) Bandmaster 6) Bandmaster from 1880 to 1931 7) Bandmaster John Philip 8) Big name in marches 9) Composer 10) Composer of many marches 11) Composer of marches 12) Composer of The Liberty Bell 13) Eponym for a low horn Found on https://www.crosswordclues.com/clue/sousa