The main purpose of a snare drum in a marching band is to provide a strong, rhythmic backbeat that drives the tempo of the performance. The snare drum produces a sharp, penetrating sound, which helps maintain the precision of the marching ensemble while ensuring synchronization among the musicians. It often plays a crucial role in cadences and other cadential passages that enhance visual formations and transitions during parades or performances. The snare drum's distinct sound contributes to the overall dynamic and energy of the marching band, making it an essential component of their musical ensemble.