Organum duplum

Organum duplum is a form of early medieval music where two vocal parts sing simultaneously. Originating around the 9th to 11th centuries, it typically involves a melody called the plainsong, sung in the lowest voice, with an additional higher voice that harmonizes. This practice marks a significant step in the evolution of Western music, showcasing early polyphony where multiple independent melodies are woven together. Organum duplum laid the groundwork for more complex compositions in later music history, influencing how choral music developed across the centuries.