From a photographic standpoint, I think the tuba section is my favourite marching band block. Aside from the fact that they usually make up the back row and are, therefore, generally pretty accessible (try getting in amongst the saxophones or trumpets, for example, and you’ll see what I mean), the huge area of brass involved in one of these instruments makes for some great reflections and pattern opportunities.
A bit of Googling tells me that legendary composer and band directory John Philip Sousa was actually instrumental (pun intended) in the development of the instrument which bears his name. It was developed in or around 1893 by J. W. Pepper under Sousa’s direction. The intent was to produce a version of the tuba which could be carried more easily while marching and whose sound was directed to carry over the rest of the band. The result was the over-the-shoulder instrument you see here.
For the technically inclined...