Many pieces are written in a minor key, meaning that they use notes taken from a minor scale. There are three types of minor scale—the natural minor scale, the harmonic minor scale and the melodic minor scale. Each has its own pattern of tones and semitones, as can be seen in the following three A minor scales. The degrees of each scale are written under the note names.
Notice the distance of 1+1⁄2 tones (three semitones) between the 6th and 7th degrees of the harmonic minor scale. This scale is often described as having an "Eastern" sound.
In the A melodic minor scale the 6th and 7th notes are sharpened when ascending and return to natural when descending. This is the way the melodic minor is used in Classical music. However, in Jazz and other modern styles, the melodic minor descends the same way as it ascends. An easy way to think of this scale is as a major scale with a flattened third degree.