ABSTRACT
Prosdocimus tuned his monochord first according to musica recta, thus acknowledging an alignment between the notional content of monochord and scale, to produce the sounds normally available and normally needed. These were then labelled with the letters of their corresponding steps on the gamut, Gamma, A-G, a-g, aa-ee, with B♭ and B♮ for all except the lowest B. He then gave two methods of deriving the ficta pitches interspersed between the rectas. The 'operation of musica ficta', that is, the substitution at any point, for contrapuntal reasons, of a tone for a semitone (or vice versa), could mean that the absolute frequency of the As, Bs, Cs that follow may not be the same as they were before, although the local interval relationships of small segments will remain intact. The taking of a conjuncta anywhere in the system may change the actual pitches following that point without changing the relationships except at that point.
