http://www.ci.bremerton.wa.us/Calendar.aspx?EID=1366
Participating musicians this year are drawn from the following 8 (yes, EIGHT!) bands: The Band of the 15th Field Artillery Regiment, Royal Regiment of Canadian Artillery (me); The Naden Band of the Royal Canadian Navy; Regimental Pipes and Drums of the Seaforth Highlanders of Canada; Navy Band Northwest; I Corps Band, Joint Base Lewis-McChord; 133rd Washington Army National Guard Band; United States Airforce Band of the Golden West; and the US Marine Corps Forces Pacific Band. As Oscar Wilde wrote, "Nothing succeeds like excess!"

Of course, each director of music wants to wave the stick, so it's going to be whack-a-mole up there on the podium, but that's showbiz!
IMBC began back in the early 1990s. There was a British Band in WA accompanying the Royal Marines on an exercise, and somebody had the grand idea that it would be fun to assemble musicians from the various military bands in the area and put on a show. It was. The concert has since alternated between Victoria, Vancouver, Bremerton, and Olympia.
This is a bit of an oversimplification, but ... the US military musicians are insanely busy just with military events, whereas the bands from north of the border tend to get to do a little more in the way of community outreach concerts. My stand partner from Navy Band Northwest last time told me that his band had been broken up into sub-groups for a month playing events, and that his entire band would not get back together as a group for another month after IMBC. The result is that while IMBC is exciting for us Canucks, for the Americans ... well, for some of them, this is the only event all year in which they get to play in a big group and blow their brains out. Needless to say, they can't wait, and their shit-eating grins are for real!
Please drop me a note if you are coming--always great to know that there is a friendly face in the crowd!