A line and a half of music added to a blank page in vol.1 ('Pars hiemalis') of the 'Glamis' copy of the Aberdeen Breviary. The music is the Tenor of a faburden setting of Cultor Dei. (Reconstructions in 2vv and 3vv are offered in the 2026 article.) Only one other faburden setting of Cultor Dei is known, on f. 159 of Cambrai MS 29.

Initially identified in 2011: "a single stave of music, four measures, on blank verso facing the first leaf of the pars hyemalis'.

Ownership inscriptions of John MacWilliam, whose father Henry was one of the 'twenty vicars of the choir' of Aberdeen Cathedral, and Nicholas Ferguson, who was appointed chaplain of St Mary's Chapel, Rattray, in 1539, link the book to Aberdeenshire until at least the 1540s.

Hand-drawn staves of 5- and 4-lines.

The Breviary is foliated, but the initial calendar section (in which the blank page with added music appears) has only a modern pagination 1-30. The music appears on the last page.