Thank you for starting these series. Has anybody on this forum an idea what the bar lines mean in the chant manuscripts of 13-15th centuries? See, for example, the 2 samples of the Communion Dominus dabit. Their placement is similar, but not identical. For example, in the upper image, the bar divides the melisma of the 1st word Do-mi-NUS. In the lower image the same melisma is divided twice. What that could mean?

It is not always easy to tell what marks were added later on, for instance:



I certainly don't pretend to know.

I'm assuming the lines (which became multiplied as time went on [see this 1818 Antiphonale] were simply the "space" for the "eyes and ears" that Abbot Pothier talked about.