Scale (music)
During the Middle Ages, and the Renaisssance, the diatonic scale (the white keys of the piano) was used most often. Black keys (called accidentals) were less common. The classical period (1600 to 1900) generally used major and minor scales, as outlined above. Natural minor was used less. From about 1900, there are other scales, for example the chromatic scale (12 half tones).