This answer by @NReilingh inspired me to trawl the web looking at Sousa music. Feeling that the clarity of orchestration contributes a significant amount to this music, I was pleased to find this original manuscript score of The Stars and Stripes Forever at IMSLP. Can anyone help me decipher what instruments Sousa has scored for (at the left of the first page of manuscript)?
Sure, he probably arranged this for other instrumentations; I'm sure his publisher and a great number of other arrangers have reorchestrated it too. But, I'm keen to find out the instrumentation Sousa originally asked for. Here's what I have so far: Db Piccolo; Oboes; Bassoons; Eb Clarinet; Bb Clarinets; Alto Sax; Tenor Sax (?); ??; ??; ??; Cornets (?); Horns in Eb; not quite sure after this, although presumably Baritone, Trombones, Tuba and Percussion (?).