This piece is a strict three-voice canon, with the lowest voice printed in red ciphers. The rubric explains that “Here follow two fugues to help you understand the music in this book, and they are in three voices. This first one shows in the following way how to understand the music (sol fa). [The note] on the third course at the first fret is middle C [ce sol faut] so that you know that the the first note in red is an A, the initial note of a melody that goes A-G-G-A-D with the black figures (starting in the other voices). And to enjoy it better, being in three voices together, he who is playing should sing the said red notes, and the second [voice] will start on the open second course, maintaining a distance of two bars, as you will see by the sign [¿] and the second voice proceeds while the third voice starts on the open first course, keeping the distance of one bar behind the second.”
The cantus firmus of this piece is based on the melody of the “Salva regina” (solemn tone), at least for the opening measures. The upper voices come in two compases after the tenor (for the alto) and one measure later for the soprano. The voices enter at the fifth and the octave above the tenor. The main modifications that occur in the upper voices are made by dividing semibreves into two equal minims.