This is the fifth motet of the cycle and its edition is also based on Librone 1 (ff. 166v–167r), where it was written by Scribe A.
The scribe made only one mistake: he wrote ‘virgine’ instead of virginis. This shows that he did not understand that the preposition de, which usually governs the ablative, in this sentence has to be referred to the word alvo (womb) and not virgo and that the sentence should read ‘born from the womb of the virgin’ (‘natus de virginis alvo’) and not ‘born from a virgin’ (‘natus de virgine’).
This motet was sung to the Sanctus and thus introduced the holiest part of the mass, namely the Eucharist. This concentration on the Eucharistic mystery is reflected in the text of the motet, which consists of a prayer to Christ, who is addressed as Saviour of the world (‘salvator mundi’) and king and creator (‘rex atque creator’). In this prayer the sinner appeals to God for forgiveness of his sins and acceptance into Heaven (‘Te deus exoro, simplex et pronus adoro / Ut mihi condones et caeli gaudia dones’). The textual source of this motet can be identified: it is a hexametrical prayer in two parts (the second part of this prayer is used for the following motet ‘ad Elevationem’) which can be found in few other manuscript sources. The first part (‘Salve salvator’ to ‘cunctis’) is found in only one further source other than Librone 1, namely the manuscript Munich, Bayerische Staatsbibliothek Clm. 641, a miscellany of secular and religious material.^[1] Interestingly, while the metrical form of the prayer is correct in the Munich manuscript, in Librone 1 we find many textual variants that allow to understand that the copyist or the person who put together the text of this motet did not detect its hexametrical structure: the variants that are most striking because they destroy the scheme are, in l. 5, the substitution of ‘sis’ for ‘fidis’ (thus a whole syllable shorter) and, in l. 7 (set in the next motet), the omission of ‘nobis’.^[2]

^[1] See Eva Ferro, ‘“Old Texts for New Music”? Textual and Philological Observations on the Cycles “Salve Mater Salvatoris” and “Ave Domine Iesu Christe” from Librone 1’, in Motet Cycles between Devotion and Liturgy, ed. Daniele V. Filippi and Agnese Pavanello, Schola Cantorum Basiliensis Scripta, 7 (Basel: Schwabe, 2019), 189–218.

^[2] Ibid.