Which term refers to medieval polyphony with a precomposed Gregorian chant and one or more additional lines?

• A. Organum
• B. Diabolus in Musica
• C. Vox Principalis
• D. Classical Singing Timbre

Answer: (A)

Organum is the medieval polyphonic style in which a Gregorian chant is laid out as a precomposed cantus firmus and one or more additional melodic lines are written above (or below) it to create harmony. In the earliest forms, the extra voice often moves in parallel intervals with the chant, producing that characteristic, drone-like texture heard in Notre Dame polyphony. Over time, composers like Leonin and Perotin expanded the approach, giving the added voices more melodic independence while the chant remains the anchor. The other terms don’t describe this approach: the diabolus in musica refers to the tritone interval, not a form of polyphony; vox principalis denotes the main voice rather than the technique itself; and classical singing timbre relates to tone color rather than a polyphonic method.