In 12th century organum, the duplum was the part immediately above the tenor. If a third part was present, it was called the triplum. In the 13th century, the duplum came to be known as the motetus. in organum, the voice above the tenor line which was the second to be composed. In early motets, this line is often called the "motetus." in the organa and clausulae the part above the tenor