The text of a clausula differs from that of the plainchant melody underneath it.
From the en.wikipedia.org
Even Stravinsky's own Russian Orthodox plainchant assumes a geometric angularity.
From the independent.co.uk
Clausulae eventually became used as substitutes for passages of original plainchant.
From the en.wikipedia.org
Their calm, slow melodies are built up from paired phrases reminiscent of plainchant.
From the en.wikipedia.org
The earliest innovations upon monophonic plainchant were heterophonic.
From the en.wikipedia.org
For several centuries, different plainchant styles existed concurrently.
From the en.wikipedia.org
Neumatic notation remains standard in modern editions of plainchant.
From the en.wikipedia.org
Like all plainchant, Ambrosian chant is monophonic and a cappella.
From the en.wikipedia.org
Newly composed music on new texts was first introduced within the context of existing plainchant.
From the en.wikipedia.org
More examples
Plainsong: a liturgical chant of the Roman Catholic Church
Also known as plainsong, chant or Gregorian Chant. Plainchant is a single melody, sung in unison by a soloist or choir, often using Latin words and a liturgical text.
Monophonic unaccompanied singing of the psalms, the Ordinary, or other sacred texts.
Or plainsong (from Lat. cantus planus) Medieval church music usually describing the Gregorian chant which still survives today in the Roman Catholic Church. It consists of a single, unaccompanied vocal line in free rhythm like speech with no regular bar lengths.