Most medieval manuscripts were first pricked in the margins and ruled before any writing of text or music occurred. In the earliest extant books with music, the space between a single ruling line was wide enough to accomodate both text and music. For example, in the Winchester Troper from around 1000 A.D. (Corpus Christi College, MS 473), sixteen points seven to eight millimetres apart in height were pricked in the margin (step 1) and the lines ruled (step 2). Text was written on each one (step 3), and then music above each line of text (step 4). In other words, no ruling line was skipped for music. But the notes tended to be smaller than the text letters.
The innovation of Guido of Arezzo and his followers was to allocate a full three or four ruling lines and to label some of these with colour and/or a clef letter. Probably in tandem with this development, an important innovation took place in Southern manuscripts: pricking patterns specifically made for music books. In the pricking pattern seen below from a twelfth-century Troper from Narbonne (Bibliothèque nationale de France, fonds latin MS 778), every fifth prick sits to the side, indicating to the text scribe that this is the line on which to write text (step 1). The folios were ruled (step 2), then came text and black notes (step 3), and finally the dry lines were coloured red and yellow (step 4).
The result of this increased space for music was a larger note; the size of text and music was now roughly the same.