Fa Fictum

FA FICTUM. In the system of Guido d'Arezzo, B♮, the third sound in the Hexachordum naturale was called B mi; and B♭, the fourth sound in the Hexachordum molle, B fa. And, because B fa could not be expressed without the accidental sign (B rotundum) it was called Fa fictum. [See Hexachord.] For this reason, the Polyphonic Composers applied the term Fa fictum to the note B♭, whenever it was introduced, by means of the accidental sign, into a Mode...