cantus firmus

[kan-tuh s fur-muh s]

noun

the ancient traditional unisonal plainchant of the Christian Church, having its form set and its use prescribed by ecclesiastical tradition.
Music. a fixed melody to which other voices are added, typically in polyphonic treatment.

Origin of cantus firmus

1840–50; < Medieval Latin: literally, firm song
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019