The source is a processionale/troper, which was written at the Augustinian monastery Grand-Saint-Bernard or in the Aosta Valley during the second half of the 15th century (cf. Stenzl 1972, pp. 152-153). This trope is notated in square notes with music for all three stanzas.
Text: Trope for the responsory “Libera me, domine, de morte eterna”, 3 stanzas of 7 decasyllabic verse lines riming abcdd|ee, formed as 5 lines followed by a two-line invocation beginning “O, O, O”; cf. RH no. 32234; edited in Clemens Blume, Tropen des Missale im Mittelalter, Leipzig 1906 (=AH 49), pp. 383-84, no. 781b. Blume remarks (p. 384) that this text probably was a reworking of the “Libera me”-trope “Dicet iustis ad dexteram positis” (no. 781a), and that it only began to appear in sources dating from the second half of the 15th century. In Knud Ottosen, The Responsories and Versicles of the Latin Office of the Dead. Aarhus 1993, it is recorded as V 173, V 231 and V 108, pp. 410-415 (all sources dated in the second half of the 15th century or later).
 Quando deus, filius virginis,
 Post hec dicet ad levam positis:
 Jam festinat rex ad judicium,
Monophonic trope setting consisting of three stanzas with the same music fully written out. After the second stanza comes a short music and text incipit ““Dum ve-”, which signals the repeat of the section “Dum venerit filius” from the responsory “Libera me”. This song must have been quite new when it was copied into the processionale at the hospice of Grand-Saint-Bernhard, since the earliest sources for the poem also stem from this period. The same tune is set with only small variants in two-part polyphony in the slightly later MS Amiens 162 D (see below). In the monophonic version the “O, O, O”-invocations are made with the help of prolonged or doubled notes instead of fermatas.
In the 4th line of the stanza 3, “nisi virgo, spes ...”, two syllables are missing; it should have been “nisi mater virgo, spes …”. The omission is hardly noticeable, because the copyist has rearranged the music, elegantly condensed it to fit the words and thereby making it a bit different from the preceding stanzas. This solution may have been offered by his exemplar, or it could be an example of performing/restructuring the music while copying.
Polyphonic setting of the tune:
Amiens 162 D, ff. 13v-16 »Quando deus filius virginis« 2v
PWCH March 2014