A work for 2 vihuelas in unison that is the only surviving example of a genre of ensemble playing where one instrument acts as a repetitive drone while the other explores the instrument as if improvising. Valderrábano explores the full range of the instrument, and various motivic and rhythmic configurations, scale patterns and the like. The rubric in the source reads in English to explain that “This music is to discant over a note or chord in a beat that is commonly called the “a tambor”. It must be played in the proportion of three minims to the bar. This sign [of congruence] is placed in the canto llano to indicate that it will always be played again [and again] until the other vihuela has finished discanting. This is the ground [canto llano] that is to be played by another vihuela in unison with the one that is to discant, or on the guitar, with its open third in the old tuning with the full [=major?] third of the vihuela in unison.