Front ensemble

In a marching band or drum corps, the front ensemble or pit is the stationary percussion ensemble. This ensemble is typically placed in front of the football field, though some groups will work the front ensemble into a tight pod onto the marching field. Some high school marching bands opt not to march any percussion instruments, but instead have a "full" front ensemble.

Originally, the front ensemble consisted of keyboard percussion and timpani, the marching versions of which are heavy and awkward. Groups began adding more and more traditional percussion instruments to the pit, and in its modern form, the ensemble may contain any type of percussion instrument from cymbals, gongs, and drum kits to Afro-Cuban percussion such as congas, bongos, claves, and cowbells, to African percussion such as djembes.

The main emphasis of the pit in drum corps style groups are the mallet instruments: marimba, vibraphone, bells and xylophone. Some marching band circuits also allow non-standard instruments (such as the violin) or electronic/electric instruments (such as synthesizers and bass guitars) in the pit. However, this is extremely controversial and divisive within the marching band community, and was prohibited outright by Drum Corps International until 2008, when it was passed in an 11-4 vote.

Pit members will sometimes operate auxiliary equipment such as props, either inside or outside of the pit area.

...
Wikipedia