Decorative Omissions
When a new chant or verse begins in Western Ms 097, the first letter of the first word of the chant is larger than the rest of the text and differentiated either by decorative designs or red or blue ink. In a number of instances, these intials are missing.
Usually, one can see a small mark in brown ink indicating what letter is supposed to have gone in that space. These marks are often visible even when the intial has been written. The writing of the colored initials must have been one of the last parts of the manuscript production process, with the scribe(s) responsible for the text and/or musical notation in brown ink having left the space and indication marks for the decorator to fill in later.
Here is an example in which the initial was filled in in red - the small brown "a" is visible towards the bottom right of the large red "A."
When the errors of omission do occur, there are often multiple on one folio. This may be because the scribe responsible for filling them in may accidentally skipped over that whole page.
Two intials are missing from folio 107r: The "L" in "Longe" and the "D" in "Deus." These were probably intended to be more simple solid-colored red or blue letters, as the more complicatedly decorated "D" earlier on the page has been executed.
Interestingly, the other side of the folio (107v) has all of its decorative initials completed. The scribe responsible for them must have had access to the physical folio but skipped over the recto side by mistake.