Rubric: “This Cum santo spirito is from the Missa ad Fugam by Josquin, it is intabulated according to these clefs” i.e. F on IV and C on III, therefore a vihuela in G. Narváez’s attribution is incorrect, however. The work is actually based on the Missa sine nomine [JosqMS, nº 17]. This is probably due to having copied the work from the Antico print (Rome, 1516) where the Missa sine nomine is misattributed as the Missa ad fugam (JosqMS, nº 16). Valderrábano set the same movement (Va125). Discussed in Bevilacqua 2004, 86-94. There is useful information on this distinctive Mass in the Wikipedia article devoted to it https://en.wikipedia.org/wiki/Missa_sine_nomine_(Josquin) {accessed 25/03/2020]