Rubric at the beginning ot the tablature says “This cantus firmus which follows goes recalling the first which says mi.fa.re.sol.fa. It should be played quite fast. Second grade [of difficulty] on a cantus firmus. This reference to the “first” is probably to the Agnus Dei setting (va003) which is a setting of the same cantus firmus. There is considrable stylistic similarity between the two works, neither of which has a strong outward appearance of polyphonic mass music. This piece is based on two statements of the cantus firmus, shown in red notes. Each cantus firmus note is reiterated for six compases. The other two voices move often much faster. In the case that it is modelled on vocal polyphony, it is possible that Valderrábano may have embellished the upper and lower parts which do start with octave imitation, but that become increasingly independent of one another as the piece proceeds. In addition to the similar setting in va003, the Benedictus of va004 also is biult from the same thematic motive, but not as a cantus firmus setting.