C

Also in the Odhecaton and numerous other sources and settings.

Passage near the end of the bassus doesn't quite make rhythmic sense. Dotted minim + minim should be two minims? Dotted minim + crotchet? Not yet clear.

Cantus waits for a very long time to enter. Effectively a solo followed by a duet. Many verses.

Can treat lower part as a canon, with second voice entering at the signum.

Round in three voices

Fallows in DIAMM facsimile edition suggests signum may indicate repeat of final section.