(Latin; " feigned music ")
In medieval and Renaissance music, the practice of inserting unnotated chromatic notes (see chromaticism ) during performances.
According to treatises of the times, it was left to the performers to "correct" certain interval s. Which intervals were to be changed, and how and under what circumstances, varied over time. This practice was responsible for the introduction of accidentals (sharps, flats, naturals) into musical notation . It also influenced the evolution of the major and minor key s on which most Western music came to be based, for it modified the medieval church mode s to resemble the major and minor scale s.