of any musical group. This includes instruments such as snare drums, tenors, 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 in most competitive circuits. Some groups will also use prerecorded sound samples such as a short jingle or a cappella singing which is typically accompanied by the front ensemble. Spoken word via microphone or a recording on a sampler is used on occasion as well. In many cases, percussion groups will use unconventional instruments including trash cans, barrels, pipes, brooms, and other objects to output desired sound effects. Concert vs. marching There are two types of indoor percussion ensembles. A concert percussion group consists of only a front ensemble. With these groups there is very little movement other than the motion needed for playing the instruments. The other type of indoor percussion group is known as marching percussion. These groups also include a front ensemble but add a marching ensemble for more movement. The marching ensembles have a much more visual aspect to their performances which includes marching, visual theatrics, and much more depending on the show theme. Marching A notable difference with marching in indoor percussion is the use of toe-down marching instead of roll stepping. Marching within indoor percussion is much more fluid in contrast with corps style marching. Due to the fact that the activity is being performed in a gymnasium means the performers are closer to the audience and requires a more fluid approach to convey the type of energy needed for a more personal performer-crowd interaction. Since each group has their own tarp with a specific design, called a floor, most groups use some type of grid to set their positions, or dots. The ensemble member is also required to 'dress' to the others, meaning to use the other marchers as a reference point and keep with formation using peripheral vision. Indoor ensembles may even incorporate dance moves and choreography into their shows for a more dramatic effect. 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