Musical notes may sound consecutive or simultaneous at any given moment of a piece of music. Music consists of horizontal and vertical aspects. The horizontal aspects of music include the melody, counterpoint, and rhythm. On the other hand, harmony is a vertical aspect of music.
A melody is a linear succession of musical notes moving rhythmically. Because of this linear movement, we consider the melody to be a horizontal aspect of music. A melody is a combination of pitch, rhythm, timbre, texture, and loudness. A melody is the foreground of a musical composition. Melodies often have one or more phrases or motifs that carry the musical ideas repeated throughout a composition in various forms. Most European music before the 20th century featured fixed, easily recognizable and recurring melodies. However, by the late 19th century, melody in Western music appeared to be the surface of a group of harmonies.
We can compose a music by just playing musical notes one after the other. However, most of the time, a piece of music consists more than just melodies. It also has an underlying harmonic structure.
The term harmony derives from the Greek word ‘Harmonia’ which means joint, agreement. In Ancient Greece, the term referred to the combination of contrasting elements such as higher and lower notes. But it is unclear whether those notes were simultaneous sounding or not. In the Middle Ages, the term referred to two pitches sounding in combination. In the Renaissance, the term denoted three pitches sounding together. Today, current dictionary descriptions of harmony often highlight the ambiguity of the term in modern use. The term harmony may refer to the combination of simultaneous sounding musical notes or the pleasing arrangements of parts. We will focus on the simultaneous sounding musical notes here. After all, the study of harmony involves chords and their relation ships to one another. First, let’s learn about consonance and dissonance.
Consonance and dissonance
In music, chords and intervals are either consonant or dissonant. The definition and perception of consonance and dissonance have varied through the centuries, as well as with the individual composers. For example, before 1300, musicians considered a third interval (C to E) as dissonant. But in modern music it is considered as an imperfect consonance. So it is important to mention that these terms are highly contextual.
Consonance is the impression of stability, sweetness, pleasantness, and acceptability. There are two types of consonances: perfect and imperfect. Perfect consonances are unisons, octaves, and perfect fifths. Imperfect consonances are minor thirds, major thirds, minor sixths and major sixths.
Dissonance is the impression of tension, harshness, unpleasantness, or unacceptability. The tension they create demands a motion to a more stable tone combination. So they need to resolve to a stable consonance. Major and minor seconds and sevenths are dissonant. The tritone is dissonant. In fact, in the Middle Ages and Renaissance, the tritone was known as Diabolus in Musica. Because the perfect fifth was considered to be a reflection of the divine, and the tritone falls short of it. All augmented and diminished intervals are also dissonant.
The perfect fourth interval can be both consonant or dissonant. In Medieval music, it was considered a perfect consonance. However, in today’s music, it is considered dissonant when not supported by a lower third or fifth.
In Jazz music, the minor ninth is too dissonant. It is the basis of the concept of the avoid notes. Typically musicians avoid the fourth note of the major scale. The reason for this is that it forms a minor ninth interval with the third note of the scale and it sounds dissonant. Musicians also avoid the minor sixth in Aeolian mode and the minor second in Phrygian mode.