While brass bands and drum and bugle corps are both musical genres which are defined by the use of instruments classed as brass and percussion, the two genres differ as follows. A brass band:
-- may or may not have an honor guard -- a drum and bugle corps must have an honor guard;
-- may or may not observe patriotic or historically military traditions and values as a drum and bugle corps must (this is due to the often strictly civilian nature of band instruments as opposed to the purely military history of drums and bugles as signalling weapons);
-- is focused first on instrumentation and the playing of instruments, not (always) first being a fraternal group, as drum and bugle corps are;
-- plays band instruments in a variety of keys - drum and bugle corps use single key brass instruments throughout their hornline;
-- may or may not play outdoors or march - while a few drum and bugle corps may be organized as a "concert" or non-marching group, they still only perform with marching outdoor instrumentation; and
-- identifies with and honors band people and band history, while drum and bugle corps identify with and honor drum and bugle corps history, all other outside musical genres being optional and less vital than one's own genre.
Some categories of brass bands, such as traditional British brass bands, observe strictly regulated rules regarding size and type of instrumentation.