During the American Civil War most Union regiments had both types of groups within the unit. However, due to changes in military tactics by the end of World War I field musical had been mostly phased out in favor of the brass bands. These performed in a concert setting for entertainment, as well as continued to perform drill and martial events. In the United States, these bands were increased in instrumentation to include woodwinds, which gives us the modern military band in the United States, as well as the basis for high school and college marching bands and concert bands.
Field music is still popular at ceremonial functions, with many organizations such as police, fire, and veterans groups maintaining pipe and drum, fife and drum, or drum and bugle corps.
In the United States Army, the band is attached to the headquarters element and one of its duties is to provide security for the command post. Regular British Army musicians are all members of the Corps of Army Music. As a secondary role they are trained to work in NBC 'Casualty Decontamination Areas'. Modern-day military musicians often perform a variety of other styles of music in different ensembles, from chamber music to rock and roll. During World War II, The Royal Air Force Dance Orchestra, better known as The Squadronaires, served to entertain troops and support morale.
In the United Kingdom, massed military bands perform at Trooping the Colour, an annual ceremonial held every June on Horse Guards Parade to mark the official Queen's Birthday celebrations.
The term "military band" may also be applied to civilian marching bands that play military-style music, march in mostly straight-line formations and have similar instrumentation. The beat of the marching band is typically 120 beats per minute, the normal military marching pace.