In European music prior to about 1600, musica ficta (from Latin, "false" or "feigned" music) referred to chromatically altered pitches, not notated in the music, which were to be supplied by singers.

Simply put, musica ficta were notes outside of the diatonic modal system in use in a given piece, and which were used to avoid harsh harmonic or melodic intervals (for example the tritone, the "diabolus in musica"). An example would be the use of a B-flat instead of a B-natural, in order to avoid a tritone against an F in another part. In modern transcriptions of Medieval and Renaissance music, these notes are almost invariably indicated with accidentals, since modern singers cannot possibly receive the kind of training given to singers seven hundred years ago; only small portions of that training can be reconstructed from fragmentary and often contradictory sources.

The exact performance practice of musica ficta, where and when they were used, is a matter of intense investigation and controversy among musicological scholars; it has been controversial, and is likely to remain so, for a long time. Music theorists from Odo of Cluny in the 10th century to Zarlino in the 16th century give highly different rules and situations for application of ficta. The controversy is not only among contemporary musicologists; theorists of the late Middle Ages were never in agreement on the rules of ficta either. 13th century music theorist Johannes de Garlandia and 14th century theorist Philippe de Vitry both wrote that ficta were essential in singing polyphony, but resisted their use in plainchant, while early 14th century theorist Jacques de Liège insisted that notes in plainchant needed to be altered with judicious application of musica ficta.

13th century theorists also divided the use of ficta into two general categories: causa necessitatis (ficta supplied by necessity, for example to avoid a dissonant interval); and causa pulchritudinis (ficta supplied for reason of beauty). Sometimes a melodic phrase simply sounds better, or sounded better to a trained 13th-century ear, when it is smoothed out by judicious application of ficta.

As an example of a related contemporary performance practice, Sacred Harp singing contains a situation similar in concept to ficta, involving the non-notated raising of the sixth scale degree in a minor mode (resulting in a Dorian inflection); new singers must be taught to do this by ear.

References and further reading

• Article "musica ficta," in The New Grove Dictionary of Music and Musicians, ed. Stanley Sadie. 20 vol. London, Macmillan Publishers Ltd., 1980. ISBN 1561591742
• The New Harvard Dictionary of Music, ed. Don Randel. Cambridge, Massachusetts, Harvard University Press, 1986. ISBN 0674615255
• Richard H. Hoppin, Medieval Music. New York, W.W. Norton & Co., 1978. ISBN 0393090906