Most Western keys are composed of 7 scale degrees, each labeled from 1 to 7. The differences between a major key and minor key are the 3rd, 6th, and 7th scale degrees. Those three notes are lowered a semitone in minor keys, which gives them a dark or somber tone to them. On the other hand, those notes are not lowered in major keys, which makes them give off a bright or cheery flavor.
