The rubric of this fantasia mentions only that “in this fantasia there are redobles to be found. Mode 5. Third level [of difficulty]. It is in the table of contents that Valderrábano adds that it “imitates one by the Milanes”, presumably Francesco da Milano. It is thus a parody fantasia, but based on one by Albert de Rippe. Valderrábano must have obtained the work from Casteliono’s 1536 “Intavolatura de Lauto” where it is misattributed to Francesco. This source was no doubt known in Spain (the design of Narváez’s Delfin is based on it). Ward [ward1953] identified the model as coming from Casteliono’s 1536 print [1536/9, nº 16, fols. 55-56v], but Ness transcribed it as No 23 in his edition of Francesco’s works. Vaccaro included it among the Fantasias of Albert De Rippe (ed. Vaccaro, no. 21). The work was published in the posthumous 1553 Le Roy edition of Alberto’s works, not published until six years after Silva de Sirenas. Robinson [robinson2014-1] reaffirms Ward and Vaccaro’s identification of the work, and agrees that the style is more characteristic of Alberto’s works and that Valderrábano must have obtained the work from the Casteliono edition. [robinson2014-1, p. 2]
The model and parody differ in structure and style. The model is more sectionalized with a greater number of clear points of imitation than the parody which is Valderrabano’s freer style. Ward (p 233) fairly accurately lists the parodied sections, which other than the opening counterpoint, are small phrases of not great consequence to the structure of the model. Valderrábano does not include the elaborate cadential and pre-cadential music of the model’s style to enunciate a form, but makes each phrase continue into the next without pause. Parody is restricted to the first 50 compases of the 114 total that is the first half. This half is largely built on borrowed material, much of it stripped of ornament by Valderrabano.

Ward gives the parodied passages as follows

Valderrábano Rippe 21
compás
1-8 1-12
9-12
13-19 13-23
19-28
29-41 27-39
42-45 86-90 (a free rendering)
46-114

The sectionalisation of the work is shown in the following diagram: