Plainsong (also plainchant) is a body of traditional songs used in the liturgies of the Roman Catholic Church. The liturgies of the Eastern Orthodox Church, though similar in many ways, are generally not classified as plainsong, though the musical form is nearly as old as Christendom. Plainsong is also commonly used in the Anglican churches. Plainsong is monophonic; it is in free, rather than measured, rhythm. Plainsong often uses the lengthy reverberations and resonant modes of cathedrals to create harmonies.