This edition is based on Librone 3, ff. 133v–135r, where it was written by Scribe I. Only one mistake can be found in this text, namely the erroneous ‘qua’ instead of quae in C and T1.
This motet is the last of the Galeazescha cycle and, as the loco rubric suggests, it was sung to the closing part of Mass, namely the Deo gratias.
The topic is once again Marian devotion and the text type that was mostly used as a text source, that of the Marian sequence. Verses 1 and 2 were taken from the sequence Virgini Mariae laudes (AH 54, no. 18, pp. 27–29), verses 3 and 4 from the sequence Ave caelorum regina (AH 54, no. 275, p. 416). A model for verse 5 can be found in the prayer Iesu parens, attested in mid fifteenth-century England.^[1] The model for verse 6 remains unidentified, but it has been connected with Duke Galeazzo Maria Sforza for the emphasis on the word Maria and the appearance of the so-called Galeazzo verset (‘Maria mater gratiae, mater misericordiae’).^[2]

^[1] See an inscription from 1451 in Julian M. Luxford, The Art and Architecture of English Benedictine Monasteries, 1300–1540: A Patronage History (Rochester, NY: Boydell Press, 2012), 88.

^[2] See Patrick P. Macey, ‘Galeazzo Maria Sforza and Musical Patronage in Milan: Compère, Weerbeke and Josquin’, Early Music History, 15 (1996), 147–212 at 164–66 and 175–80, later qualified by Nolan Gasser, ‘“Beata et venerabilis Virgo” : Music and Devotion in Renaissance Milan’, in Sally McKee (ed.), Crossing Boundaries: Issues of Cultural and Individual Identities in the Middle Ages and the Renaissance (Turnhout: Brepols, 1999), 203–38 at 215–22.