Throughout the period that incorporated musica ficta, singers sight read melodies through a series of interlocked hexachords that formed the backbone of the solmization system-a method that eventually became the modern system of tonic solfa.
However, in the 16th century, the signs used to represent these fictive notes (the signs for b mollis [] and b durum []) came to acquire their modern meanings of raising or lowering notes by a half step .