Musica ficta
Musica ficta (from Latin fingere, PPP fictum "to shape, form"; also musica falsa from Latin falsus "imitation, inauthentic"; Engl. roughly "deviating tone") was the term used in music theory from the beginning of the 13th century onwards to describe those tones which, according to the solmization system, do not occur in a hexachord. The term "falsa" was used in music theory from the beginning of the 13th century to describe those tones which, according to the solmization system, do not occur in a hexachord 
and can only be reached by means of transposition signs ( and 
) or transposition of the hexachord to an uncommon starting tone. The term initially referred to the hexachord alone, and later to scales as well. One reason for this was the avoidance of the tritone as a diabolus in musica, from which the interval designation falsa quinta (roughly: "altered fifth") also derives.
Until the 14th century, the term falsa, which had been handed down until the 11th century, was used until the term ficta began to assert itself against the background of changes in musical practice. The attribute falsa persists into the 16th century, e.g. in Gioseffo Zarlino, but is used more for interval relationships. This view of notes foreign to the ladder, which were not notated anyway and only appear in the musical text in modern editions, as "unnatural" in the sense of the hexachord system, stands in contrast to contemporary vocal and instrumental music. Organ music had already used all chromatic semitones since the beginning of the 12th century.
The practical use of fictae thereby distinguished the causa necessitatis (Latin for "necessity"), in order to avoid dissonance in the contrapuntal movement, from the causa pulchritudinis (Latin for "reason of beauty of tone") due to the composer's aesthetic considerations. With tempered tuning, the term finally lost its meaning in the 16th century.
Questions and Answers
Q: What is musica ficta?
A: Musica ficta is a term used in medieval and Renaissance music where musicians play or sing music putting in accidentals (sharps and flats) which are not written in the music.
Q: Why did musicians use musica ficta?
A: In those days, music used modes instead of the modern system of major and minor keys. Sometimes the music would not sound right unless a note was sharpened or flattened (raised or lowered a semitone).
Q: What is an example of musica ficta?
A: To go down from the note B to an F would have sounded bad, so the F would need to be an F sharp. The composer who wrote the music down might not bother to put the sign for F sharp.
Q: Why did composers start writing exactly what notes they wanted?
A: Gradually it became more and more necessary for composers to write exactly what notes they wanted. The modern system of keys was developing. They developed the system of key signatures and accidentals (sharps and flats which are not in the key signature, but written as and when they are needed).
Q: What happened to the practice of musica ficta?
A: The practice of musica ficta gradually ended.
Q: When was the modern system of major and minor keys developed?
A: The modern system of major and minor keys was developing near the end of the 16th century.
Q: What are accidentals in music?
A: Accidentals in music are sharps and flats that are not in the key signature but written as and when they are needed.
