FICTA (FALSE), MUSIC. - The expression "musica falsa" certainly exists in the first half of the 13th century, since around 1250 Pseudo-Aristotle
(Magister Lambertus) treats of it and proposes replacing the expression "falsa" with "mutata." Later, m. f. was preferred. The reason for the "falsity" or "feigning" consists in this: that while in "true" music one sings according to the intervals marked by the notation, in "false" music these intervals are changed or altered by lowering or raising them by a semitone by means of the flat and the natural, placed outside their normal position, that is, B: hence falsity, because the sign of the mobility of B is moved outside its true seat; falsity also because what is sung is not what is read as written, the key signature being unknown in the Middle Ages; at most, rarely, mention was made of the necessity of falsifying by adding the natural and the flat above the note to be altered; but normally the singer had to know the rule and apply it even without written indication. The origin of the theory of musica falsa is closely linked with the use of solmization and the development of polyphony. On the one hand, until the introduction of the monosyllables (ut, re, mi or others), it was neither necessary nor even possible to make "mutations," that is, in short, to call every semitone mi fa; "false" music will precisely cause mi fa to be sung even when a semitone is not written.
Music theory before c. 1030 knows no semitone other than B (natural) to C, plus the semitone inherited from the Greeks under the name of synæmmenon, that is, B-flat, acute, also marked in medieval musical diagrams with the letter S. In practice, however, use is also made of the low B-flat and even of two other movable notes, E, which can be flat, and F, which can be sharp. But this must not be ascribed to the practice or theory of m. f., and even less to a chromaticism in the modern sense; it results from the simple play of transpositions of formulae and moduli, and, given the imprecision of medieval modal theory, this play was not brought into evidence except in the passage from "in campo aperto" notation to notation on the Guidonian staff (e.g., the introit "Exaudi Domine vocem meam," which, if transposed a fifth lower, carries an E-flat at the beginning; if written on final la, it should be sung with F-sharp).
The discussions of medieval theorists before the 12th century demonstrate that for them the word musica falsa and the concept itself are unknown. If the division of the monochord yields some sound not insertable in the series of the seven diatonic sounds, the theorist excuses himself for it as a consideration of purely speculative interest (cf. the De musica of the 11th century, not to be attributed to St. Odo of Cluny [Gerbert, I, p. 274]: an unusual letter "m" indicates this sound, which constitutes C, or F, or mi; or it is intercalated between C and D, between D and E, between F and G). Sometimes the theorist simply condemns the displacement of the semitone and calls it "absonia" (cf. Hucbald, Musica enchiriadis: Gerbert, I, pp. 176-77).
On the other hand, from the examples given with the first texts that report the word "musica falsa," one sees that this mutation was resorted to with the intent of obtaining perfect consonances and above all of avoiding making the extreme notes of the tritone heard simultaneously.
It must be observed, however, that the number of scales, or rather of hexachords, originating from musica falsa does not multiply; the most used are: begin{array}{l} B♭ - C - D - E♭ - F - G \ E♭ - F - G - A♭ - B♭ - C \ D - E - F♯ - G - A - B \ A - B - C♯ - D - E - F♯ \ E - F♯ - G♯ - A - B - C♯ end{array}
The importance of this fact of musical practice, also explained by theorists, must not be minimized; it marks a stage between the diatonicism, more or less rigid, of Gregorian melody and the appearance of tempered scales; it is in direct relation with the modal character of polyphonies and music before the 12th century and authorizes in many cases the precisions given by some editors of ancient music to the notes that according to classical criteria should be altered.