Music Theory

Introduction

The study of music theory deals with the interactions of the basic components of music (harmony, melody and rhythm) as a means to a creative end. What this means specifically varies from culture to culture and even listener to listener. In an academic context, music theory almost exclusively refers to the Western system of equal temperament.

Certainly there are specific combinations of chords, melodies and rhythms that humans innately find pleasing. Indeed, there is no civilization on earth that does not play some kind of music. But what specifically qualifies as 'pleasing' varies wildly. For instance in Western music, once a tonal center has been established, the 7th scale degree will always have a tendency to resolve upward and the 4th downward. Music theorists expose these patterns in order to understand them and use them more effectively in their own compositions. Very frequently these endeavors show the underlying principles that are shared by all Western music and are therefore also used by music historians to determine the 'genealogy' of the various musical genres.

Harmony

Harmony is the vertical analysis of a series of pitches played in simultaneously. The basis for all Western music are 12 equally tempered half steps. The most basic arrangement of these 12 pitches is called the major scale. This is a major scale in the key of C:

C        D        E        F        G        A        B        C
I          ii         iii        IV       V        vi        viio     I

By stacking a third and fifth onto each note of the scale, one can see all the possible diatonic chords in the major scale. A diatonic chord is a chord which contains no notes outside of the scale. The Roman numerals underneath each note name represent what type of chord is formed when a third and a fifth is stacked on the scale note. A capitalized Roman numeral represents a major chord, a lowercase Roman numeral designates a minor chord and the seventh is always diminished. The analysis shown above is in the key of C; however, when transposing to another major key, the Roman numeral analysis will always stay the same. In other words, in the key of A, ii iii and vi are still minor; they are just B minor, C# minor and F# minor instead of D, E and B.

Now, let's add another third on top of the fifth we already placed on each of the notes in the scale. This gives us the diatonic seventh chords in the key.

Cmaj7    Dmin7    Emin7    Fmaj7    G7    Amin7    Bdim7

Despite the staggering number of options, the I, IV and V chords are the most widely used. They are found in all types of Western music but certain styles contain these chords nearly exclusively. For example, a standard 12-bar blues progression will only use these three chords, although sevenths may be added.

One of the distinguishing characteristics of Western music is that there is one tonal center occurring at a time. It can change throughout the song (this is called modulation) but only one will exist at a time and exists as a reference for every other note played. This is true in the vast majority of cases, the exception being certain 20th century avant-garde pieces. However, a major scale is not the only way to establish a tonal center.

Modality

Derivations of the major scale, called modes, can provide variety. A mode is obtained by first starting with a major scale and displacing the tonic to another scale degree. A regular major scale like the key of C could then be called C Ionian. Let's take a look at the others.

C Ionian - C D E F G A B C
D Dorian - D E F G A B C D
E Phrygian - E F G A B C D E
F Lydian - F G A B C D E F
G Mixolydian - G A B C D E F G A
A Aeolian - A B C D E F G A
B Locrian - B C D E F G A B

In this way we can see that Ionian is just another word for 'major' and Aeolian is just another word for 'minor'. These 7 scales comprise the vast majority of the music we hear on a day to day basis. In the majority of cases, the modes are used compositionally as a way to introduce variety to an otherwise bland chord progression. By giving a quick taste of a parallel mode, one can keep music interesting and compelling. This is called modal interchange and it is a type of brief modulation. It is very frequently used in a major key context with chords from the parallel minor. This is especially true in rock music. Other modes which are frequently 'borrowed' from in this way are lydian and mixolydian.

Cadence

A cadence is a harmonic movement which ends a passage and returns the listener's ear to a state of 'rest'. The common type of cadence is called a dominant cadence. This is universal to all Western music and is heard in classical music, folk, reggae, the blues and everything in between. It occurs when the V chord resolves to the I chord. Even people with no musical training can hear this cadence as providing 'closure'. It is an essential component of Western harmony. Other types of cadences are possible.

Authentic      IV > V7 > I
Dominant     V7 > I
Plagal           IV > I
Half                x > V
Deceptive      V > Anything but I

When all of the chords in an authentic cadence are in root position (the root of the chord is in the bass), it can be called a perfect authentic cadence.

Consonance

Consonance and dissonance cannot exist separately from each other. Much like happiness and sadness both must be experienced to make sense of either of them. The goal of music is not to be universally and constantly consonant. What composers have discovered over the years is that their job is a much more complex one. Indeed, they must balance moments of consonance and dissonance in order to evoke an emotional reaction from the listener. Some styles of music hold dissonance in higher esteem than others. Pop music very frequently contains no non-diatonic pitches or chords, while jazz makes freer use of notes outside the scale.

Melody is a succession of pitches, as opposed to harmony which is a simultaneity. Melodies are a powerful thing; indeed, a good melody can be passed on culturally as a meme. A particularly striking melody can have a concert goer humming the tune long after the last note of the show has been played. Perhaps the reason why melodies linger in most people's heads more often than, for instance, chord progressions is debatable. But one thing is clear -- melody and language are intimately related, and it is possible our brain processes them similarly. Indeed, melodies contain phrases that, much like speech, are paced with the musical equivalent of commas, semicolons and periods. Most melodies follow the path which the chords cut out for them. If when analyzing a piece of music a specific note of a melody is also contained in the chord which is simultaneously being played, this melody note is called a chord tone. If the note is not contained in the chord it is then called a tension. Even if the melody notes are not contained in the chord, in order to have a coherent piece of music, the melody and harmony must work toward the same end.

Rhythm

Rhythm may be the most ancient element of music in existence. Although it is possible to have a song without a melody or chords (harmony), it is hard to imagine a song with no rhythm. The arrangement of sounds in time is the basis for music and rhythm is inextricable from that definition. Beats are arranged into regular pulse groupings which usually stay consistent for the length of a song. Any change in the basic subdivision of rhythm in a song is called metric modulation. The difference between rhythm and meter is subtle. Rhythm refers to a pattern of duration; meter refers to the smallest underlying subdivision of time that we hear in music, and how rhythms are laid over it. The most common subdivision of beats in Western music is 4/4, meaning 4 beats in a measure, each beat being represented by a quarter note. This is called a time signature and is always specified at the beginning of a notated piece. A waltz is by definition in 3/4, and is another common metric subdivision. Also in common usage today are 6/8, 2/4, 9/8 and 12/8.

Syncopation

In many cases, the attack and release of a rhythm will occur directly on the beats in a song. When the attack occurs between beats, this is called syncopation. While syncopation is found in all styles of music, it is especially prevalent in reggae, where it forms an important part of the backbeat. Jazz is another genre that makes extensive use of syncopation.