cantus firmus

 
Pronunciation: /ˌkantəs ˈfəːməs/

noun (plural cantus firmi /ˌkantuːs ˈfəːmʌɪ/)

Music
  • a melody used as the basis for a polyphonic composition: this four-part mass uses as its cantus firmus a popular French tune

Origin:

mid 19th century: from Latin, literally 'firm song'