Fantasia on an ostinato cantus firmus: fa mi ut re (F–E–C–D). The theme (4 tab. compases) proceeds throughout piece without any free episodes, swapped around between each of the voices. The writing is mostly in duo with free counterpoint above the cantus firmus, however, a considerable amount is in trio but with only one voice at a time in short note values. The theme is short and distinctive. Shape is given to it by the accompanying free part that seem almost extemporised. Compases 14-16, 33, 36-39, 60-64 have a 4th voice added. The tempo is Apriessa (fast)
Bars: 1-24: Theme occurs 7 times in original position alternately in Cantus and Tenor. – always in Semibreve
Bars 25-28: Appears in bass, transposed up a 4th, in Semibreve
Bar 29: free – (modulation)
Bars 30-36: Tenor then Cantus, transposed down a 4th, in Semibreve
Bars 36-39: Cantus returns to original position with transposed figure in bass 35-37. More homophonic effect, slight modification of themes.
Bars 39-52: Continually in lowest sounding voice, once transposed up a 4th, and 42-45 down a third to accompany theme in Cantus in parallel 10ths.
Bars 49-59: Three repeals in O in long values Semibreve in tenor.
Bars 60-63: Coda with partial repeat in 61-62 in Bass transposed.

Overall Scheme:
1-36: Theme brought out in 1st or 2nd voice; long notes: 1 voice leading at a time.
36-39: Short homophonic like passage
39-63: 1 statement in Cantus then only in lower voices with cantus making one long line in contrast to the previous short phrases.

Venegas de Henestrosa reworked this fantasia. See 1557/2, no. 58 [Anglés edition, p. 82, Fantasia IV]