A leaf from a Ferial Psalter, in Latin, illuminated manuscript on vellum [?Spain, c.1500]

From an imposing, large-format Spanish Ferial Psalter.

c.580 x 410mm. The recto with 9 lines of text and 6 of music on a 3-line stave, the large illuminated initial 'N', with foliate extensions, opening the Ferial office for Thursdays 'Nox atra rerum contegit'; the verso with 16 lines of text and one of music on a 4-line stave, the large illuminated foliate initial 'S' extending into the margins and opening Psalm 68: 'Salvum me fac Deus quoniam intraverunt aque', smaller initials in red or blue, the second letters after the illuminated initials calligraphic, rubrics in red (some cockling, else in excellent condition). Mounted and in a double-sided frame.