From wikipedia.org:
A drum and bugle corps or drum corps is a musical marching unit (similar to a marching band) consisting of brass instruments, percussion instruments, and color guard. The activity originated in the United States and Canada, but has spread to parts of Europe and Asia. Typically operating as independent non-profit organizations, drum corps perform on-field competitions, parades, festivals and other civic functions. The prime age for participation is 14–22, but the activity extends throughout age groups younger and older. Competitive corps participate in summer touring circuits. Competitions occur on football fields and are judged based upon general effect, visual performance, and musical performance. Every year, each drum corps prepares a single new show, approximately 8–12 minutes in length, and carefully refines this throughout the entire summer tour. This focus on a singular show takes advantage of the large amount of time needed to honing and refining a modern drum corps program, with a momentum that continues to build up to the last performance of the season. Musical repertoires can vary widely among shows, including symphonic, jazz, big band, contemporary, rock, wind band, vocal, Broadway, Latin music and many other genres. Highly competitive corps regularly dedicate 8–10 weeks on tour, practicing and performing their program full-time. Less competitive corps have less demanding schedules, allowing members to participate and still have a little free time outside drum corps. Some corps are not competitive at all, serving as education for youths, as alumni corps for adults, or for other traditional civic functions.