Indoor percussion ensemble
An indoor percussion ensemble or indoor drumline consists of the marching percussion (or battery) and front ensemble (or pit) sections of a marching band or drum corps. The only exceptions are in concert divisions (e.g. Percussion Scholastic Concert Open ) where the marching line is absent and the ensemble consists entirely of a pit. Indoor Percussion marries elements of music performance, marching, and theater; thus, the activity is often referred to as percussion theater. Although most indoor percussion ensembles are affiliated with high schools, there are also many independent groups that draw participants from a large area. Independent groups typically start rehearsing in October and groups associated with high schools start after marching band season ends in November or December, and the season culminates with WGI World Championships in April. It is sometimes called Winter Percussion due to the season in which it mostly occurs.
Indoor percussion (Drumline) began in 1969 at the Dassel-Cokato High School in Cokato, Minnesota, pioneered by the schools band instructor Steve Johnson. Their show "At the Dawn of War" attracted many national as well as international musicians, specifically percussion experts. The athletic arts were looking for a new intriguing sport that could challenge and excite skilled musicians, so they started creating their own styles all over the world. Over the past 30 years, marching percussion has advanced and moved into auditoriums and gymnasiums as percussion ensembles looked for ways to maintain their skills during the winter months when performing outdoors on football fields was not practical. Following in the footsteps of indoor guard ensembles, indoor percussion ensembles arrange music and motion appropriate for a more intimate setting. The activity is enjoyed throughout the United States and Japan, as Winter Guard International (WGI) provides many regional and national opportunities to compete. Percussion ensembles first appeared in WGI shows in 1992, and the theatrics, sets, and music selection has advanced throughout the activity's history. There are many organizations unaffiliated with WGI that hold smaller regional shows.
Competitive groups are held to specific times and judged on criteria that change every season as technology and creativity blossom. These ensembles compete, but traditionally, the musical sport is treated as a place to grow together as a community, learn new techniques, and enjoy the work done by peers from across the country and locally.
Competition became international when Color Guard Netherlands (CGN) introduced Indoor Percussion in Europe. In 2008 CGN hosted the very first WGI Regional for Percussion outside of North-America.
Music is arranged based on original works, as well as recreations of movie themes, popular music, classical music, and more. Instrumentation is anything that would or could be used under the percussion category of any musical group, including: snare drums, tenor drums or quads, bass drums, cymbals, xylophones, marimbas, vibraphones, tambourines, chimes, timpani, drum kits, and other similar instruments. Electronic instruments such as guitars, bass guitars, theremins, and synthesizers are also allowed - however, no prerecorded music may be played. Spoken word via microphone or a recording on a sampler is used on occasion as well. Unconventional instruments such as trash cans, barrels, pipes, brooms, and other things that make percussive sounds are sometimes used.
A notable difference with marching in indoor percussion is the more frequent use of toe-down marching. Marching within indoor percussion is much more fluid in contrast with corps style marching and is much more group dependent due to the lack of yard lines. Rather than relying on yard lines to guide placement, the marcher is required to 'dress' to the others, meaning to use the other marchers as a reference point and keep with formation using peripheral vision. Some indoor ensembles even incorporate basic dance moves into their shows for a more dramatic effect.
Concert ensembles perform using only pit instruments, removing the marching element from the show. A drumset is often incorporated into the pit to make up for the lack of battery instruments. These indoor groups have come under hard fire in the last couple of years as to whether they should stay in the WGI circuit. In The Netherlands not only Concert groups can compete, also standstill drumlines can compete in the Standstill Class.
Set designs 
Depending on the financial situation and the creativity of the design team, sets can be created to help the audience engage the performance to a greater depth. Painted floor coverings and backdrops are used to portray a story as the group performs the music in and around the props. Most upper level groups have large nylon-vinyl tarps that cover an entire gym floor.
Sets must also be designed to function within the space provided. If a performance is in a gym, the materials must be able to enter the gym. If the performance is in a stadium type gym, then doors and openings are easier to access.
There are strict rules on the area sets can be placed on and the time a group is allowed to set them up. Violations of these rules result in score deductions.
At first, indoor percussion ensembles wore traditional marching band uniforms. As shows and concepts increased in detail, uniforms were left behind, and theatrical costumes took their place. Uniforms could be as simple as jeans and t-shirts for a rendition of West Side Story or as complicated as special jumpsuits with chains and feathers to portray a show like Cirque Du Soleil, though many groups use more modern uniforms.
Influence on drum corps 
Some drum corps, most notably The Cadets, have attempted to make their outdoor field shows more intimate and theatrical like indoor percussion shows. The Cadets have taken ideas pioneered indoors to the field, such as the "Gods of Quads" tenor feature by Ponderosa High School from Colorado, and "drum speak" feature originally developed by the Mission Viejo High School Mission Viejo, California indoor percussion ensemble.
Winter Marching Ensembles 
A more recent development in the Indoor Percussion Ensemble genre has been the introduction of mixed-group ensembles, combining Winter guard with Indoor Percussion Ensembles, sometimes referred to as Winter Marching Ensembles, most notably the Aimachi Ensemble based out of Japan.
Indoor Drumline Circuits 
- WGI (Winter Guard International)
- IPE (Indoor Percussion Europe)
- IPA (Indiana Percussion Association)
- AIA (Atlantic Indoor Association)
- RMPA (Rocky Mountain Percussion Association)
- MEPA (Mid-East Performance Association: Ohio, Kentucky, Indiana)
- OIPA (Ohio Indoor Performance Association)
- SCGC (Southeastern Color Guard Circuit)
- PASIC (Marching Festival)
- ADLA (American Drumline Association)
- MPA (Minnesota Percussion Association)
- KIDA (Keystone Indoor Drill Association)
- SCPA (Southern California Percussion Alliance)
- MCGC (Michigan Color Guard Circuit)
- NYSPC (New York State Percussion Circuit)
- MCCGA (Mid Continental Color Guard Association)
- FFCC (Florida Federation of Color Guards Circuit)
- TCGC (Texas Color Guard Circuit)
- TRWEA (Three Rivers Winter Ensemble Association
- NESBA (New England Scholastic Band Association)
- MAPS (Mid-Atlantic Percussion Society)
- SAPA (Southern Association For Performance Arts)
- CWEA (Carolina Winter Ensemble Association)
- CGN (Color Guard Netherlands)
- MCCGA (Mid Continent Color Guard Association)
- GCGC (Gulf Coast Guard and Percussion Circuit)
- CCGC (California Color Guard Circuit)
- PPAACC (Pep & Pageantry Arts Association of Central California)
- WGPO (Winter Guard and Percussion of Oklahoma)
- CIPA (Carolina Indoor Performance Association)
- USSBA (US Scholastic Band Association)
- NCBA (Northern California Band Association)
- MIA (Mississippi Indoor Association)
- UWDA (Utah Winter Drumline Association)
- CBA (Cavalcade of Bands Association Indoor)
- SJVCGPR (San Joaquin Valley Color Guard and Percussion Review)
-  (Legacy Indoor Percussion, Indiana's ONLY Independent World Class Indoor Drumline)
-  (NorthCoast Academy Percussion Ensemble)
-  (Redline Percussion)
-  (Insight Percussion Theater, Louisiana's only Independent Open Ensemble)
- Drumline Chops: An Educational Website for Rudimental Drumming and Marching Percussion
- A Comprehensive List of Marching Percussion Ensembles
- TOB Info (Tournament of Bands for Tournament Indoor Association)
- PercussionMedia - Huge archive of percussion, drumline, and WGI videos
- Incognito Independent Drumline (Incognito is based in Southern California)
- Norristown Indoor Percussion Ensemble (An example of a High School World-Class Indoor Percussion Ensemble)
- Penn State Indoor Drumline (Penn State University's Indoor Drumline)
- Breakthrough Indoor Percussion (WGAZ & WGI Independent Open Indoor Drumline from the Phoenix, AZ metro-area)
- Dark Sky Percussion (independent percussion ensemble from Scottsdale, Arizona)
- Perc Up! (Perc Up! Percussion Music Education Resource, Clinics and Showcase)
-  (IPA - Indiana Percussion Association)
-  (WGI - Winter Guard International)
-  (CWEA- Carolina Winter Ensemble Associtaion)
- (CVGPC- Central Valley Guard and Percussion Circuit)
-  Tournament Indoor Association