 Chromatic most often refers to structures derived from the twelve-note chromatic scale, which consists of all semitones.Historically, however, it had other senses, referring in Ancient Greek music theory to a particular tuning of the tetrachord, and to a rhythmic notational convention in mensural music of the 14th through 16th centuries.In ancient Greece there were three standard tunings (known by the Latin word "genus", plural "genera") of a lyre.