An indoor percussion ensemble or indoor drumline is a type of marching ensemble consisting of battery and front ensemble instruments. It differs itself from a traditional percussion ensemble by not only on musical performance, but on theatrics and marching. Although most indoor percussion ensembles are affiliated with high schools, there are also many independent groups that draw participants from a large area and are independently funded. Independent groups typically start rehearsing in October, while high school groups typically start after their fall marching band season ends. Because of this, the activity is often called winter percussion or winterline.

Marching percussion instruments are percussion instruments specially designed to be played while moving. This is achieved by attaching the drum(s) to a special harness worn by the drummer, although not all marching bands use such harnesses and instead use traditional baldrics to sling their drums.