A series of twenty-six parchment binding reinforcement strips cut horizontally from bifolios of a musical manuscript, preserved in situ as sewing guards at the center of folio-sized paper gatherings (mostly sexterns) of a 1469 manuscript volume of collected writings of Thomas Aquinas. The host volume measures 29.5 x 21.5 cm, and the strips are nominally 29cm in width, with a stave gauge of approx. 12-14 mm. The original leaves contain anywhere between nine and eleven staves, depending on the music being accommodated. The strips are located between 7v-8, 19v-20, 31v-32, 43v-44, 55v-56, 67v-68, 79v-80, 91v-92, 103v-104, 115v-116, 127v-128, 139v-140, 151v-152, 163v-164, 174v-175, 185v-186, 197v-198, 209v-210, 221v-222, 233v-234, 244v-245, 255v-256, 267v-268, 279v-280, 291v-292, and 302v-stub at the back of the volume.

Together the strips comprise two bifolios: one complete (fourteen strips, hereafter bifolio A) and the other (twelve strips, hereafter bifolio B) missing two contiguous strips in the upper-middle portion. The missing strips of bifolio B accommodated approximately one stave and two lines of text. The bifolios preserve their original medieval foliation in Arabic numerals; these read 44 and 57 for bifolio A and 45 and 50 for bifolio B. The four leaves transmit eleven compositions (or parts thereof): six Mass Ordinary settings, four Latin motets, and and one French-texted chanson used as filler at the bottom of f. 50. Two of the motets are unique (Devorato/Requiem/Lux, and Plaude/Comes/Alleuya), and two provide concordances for known motets (Vos/Gratissima/Gaude and Aucuns/Amor/Kyrie). Two of the six Mass Ordinary settings are unique and four are known from B-Tc A 27 (Mass of Tournai) Among the Mass Ordinary settings are canonic Sanctus and Agnus Dei settings (conceivably a related pair), both complete; the former provides a first concordance of the canonic Sanctus known from Tournai, and the latter unique. The remaining four Mass settings are notated in three-part score (with voices labeled a, b and c in the margins) and are all incomplete bar the Agnus Dei from the Mass of Tournai. The unique setting is a Gloria.

The strips were mentioned in Christina Meckelnborg's 1998 inventory of the manuscript holdings of the Koblenz Landeshauptarchiv, though their actual musical content was not accurately described in detail. These strips are undoubtedly from the same original musical manuscript as some of the the fragments preserved in Best. 701 Nr. 243 in the same archive, discovered by Karl Kügle. Both host volumes originally belonged to the library of the Carmelite monastery in Boppard. (For details on the ownership of Best. 701 Nr. 243 see Kügle, Karl. 2018. Vitry in the Rhineland: new discoveries. Early Music, 46 Issue 3: 393–402, as well as that source's entry here on DIAMM.)

Discovered by Richard Dudas, October 2025.

Music in this source is notated both with minim stems and dots of division to delineate groups of semibreves and minims. In a few places, the addition of minim stems was inadvertently overlooked, suggesting some of the music in this source might have been copied from exemplars notated undifferentiated semibreves and dots of division. With the exception of the apparently later-added chanson at the bottom of f. 50, no distinction is made between semibreve and minim rests – these are indiscriminately written hanging from, sitting on or bisecting stave lines. For voice parts of pieces in perfect modus whose rhythms move in longs and breves, the length of notes (subject to the rules of imperfection and alteration) is often clarified by a series of one, two or three dots placed above the note form.