The harmonic scale is a musical scale that follows a specific tonal pattern. Like most major musical scales, the harmonic contains seven notes and repeats every octave. While it is less used in musical composition than the diatonic scale, the major and minor versions of the harmonic scale are seen in jazz, some pieces of the 16th-19th century, and occasionally to mimic a Middle Eastern scale.
In music, a major scale consists of a seven notes that follow a specific pattern of whole and half step increases in pitch. A diatonic major scale’s pattern is two whole steps, one half step, three whole steps, one half step. In the key of C the sequence involves no sharp or flat notes. This key is easy to play on a piano, as they are laid out to match a C major scale exactly. A major harmonic scale is nearly identical, with the only difference being that the sixth note is flattened by one half step.
A minor scale is essentially a major scale with the third note flattened by one half step. Consequently, the harmonic minor has both the third and sixth step flattened. This scale is particularly disturbing to those only used to hearing the diatonic major and minor scales common in Western music. The harmonic minor scale is also called the Mohammedan scale, as it is similar to a popular scale in music of the Middle East. Because most Eastern music involves quartertones, which Western instruments cannot be tuned to, the harmonic minor is one of the only scales that can be mimicked in Western music.
If you are used to Western music and are not a trained musician, the harmonic scale can sound very off-putting at first. It is difficult to play as chords on the guitar, as it requires a major shift in chord structure halfway through the scale. It can also be tricky for vocalists, as the flattened sixth note is a highly unusual component of most vocal music.
Emotively, harmonic scales are generally said to evoke sadness or eeriness. Harmonic minors are often used to augment the harmony component of minor chords, although a diatonic minor is used to create the melody. Musical experts usually refer to the harmonic scale as having a strong or intense sound. With few exceptions, the harmonic scale is not generally sustained throughout an entire piece of music, but used rather for emphasis. For composers, the harmonic scale allows nuance and texture to be added to a piece, to draw attention to specific musical themes.