Musica ficta
Musica ficta (from Latin, "false", "feigned", or "fictitious" music) was a term used in European music theory from the late 12th century to about 1600 to describe pitches, whether notated or added at the time of performance, that lie outside the system of musica recta or musica vera ("correct" or "true" music) as defined by the hexachord system of Guido of Arezzo. == Modern use == Today, the term is often loosely applied to all unnotated inflections (whether they are actually recta or ficta notes; see below) that must be inferred from the musical context and added either by an editor or by performers themselves.