| Theory of Harmony - An Overview
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Here's a brief overview of the Theory of Harmony. Could be of interest, to people new to music and bass guitar.
Source: Encarta
Harmony
Harmony is the combination of notes (pitch) that sound simultaneously. Has two definitions, which include:
- Sequence of simultaneously sounded pitches chord progression.
- Single instance of pitches sounding together chord.
Harmony stands in contrast with Melody (pitches sounding one after another creating tension). With melody and Rhythm (tension and duration of sound), Harmony is one of the three main elements of music. Has assumed the central role in musical structure and expression. Also, Harmony is known to be tonal, which has a central, or home tone called the Tonic.
Intervals and Triads
Interval refers to the distance between two musical pitches, and are the building blocks of harmony. Intervals of different sizes (distance from Tonic note) have different qualities, these include:
- Consonance: blend well together.
- Dissonant: two notes that clash, often creating and expectation that they will resolve to consonance.
In fundamental harmony is the triad (unity made up of three parts). Triad is a three note chord that sounded simultaneously. Example: Root, Third, Fifth.
- Triads exist in four main variations:
- Major Triad (consonant): C-E-G
- Minor Triad (consonant): C-Eb-G
- Diminished Triad (dissonant) C-Eb-Gb
- Augmented Triad (dissonant): C-E-G#
Keys
In functional harmony, in order for a pitch to be tonic, it must be the central focus of a group of pitches. There are two main groups of pitches Major and Minor scale groups. The key of a scale group, is the Tonic note with its scale notes. Triads can be built on any note of the scale. In the Roman Numeral System, each scale note is allocated a number. Example for Major triad:
- C (root): I
- E (third): III
- G (fifth): V
Triads can be sounded with any note at its bass. This is called Triad Inversion. Example inversion for the Major triad:
- E-G-C: where E is the bass note.
- G-C-E: where G is the bass note.
- C-E-G: where C is the bass note.
Harmonic Progressions
Movement from one chord to another is called a harmonic progression. This creates the sense of motion. Simple harmonic progression can include, departure from the tonic (I) chord, and motion leading to dominant (V) chord. Progression endings are called Cadence, where progression may end on tonic (I) chord. Within progressions, accented beats are used in coordination with points of harmonic change.
Diatonic and Chromatic Harmony
Harmonies and harmonic progressions that only use the notes of a given key are called Diatonic. Chromatic notes are notes outside of the key. Chromatic notes can be used to modify chords and harmonic progressions. Tonicization is the process by which a change in key is used to obtain a temporary tonic. Modulation is the process when the key is permanently changed in a progression.
Non-harmonic Tones and Dissonant Chords
Harmonies provide a foundation by which melodies are constructed. Melody notes can be harmonic or non-harmonic (external). Non-harmonic tones can decorate pitches that are members of that harmony. Seventh chords are harmonic triads with seventh notes added above the root. The Seventh note are non-harmonic tones that decorate triads. These types of chords are known as dissonant chords. Non-harmonic tones can melodically connect chords together.
Categories and Names of Tonal Chords
Most common chords are triads and sevenths chords
- Diminished + Seventh: C-Eb-Gb-Bbb
- Half Diminished + Seventh: C-Eb-Gb-Bb
- Minor + Seventh: C-Eb-G-Bb
- Dominant Major + Seventh: C-E-G-Bb
- Major + Seventh: C-E-G-B
Functional Chord Names
I Tonic
II Supertonic
III Mediant
IV Subdominant
V Dominant
VI Submediant
VII Leading Note
Chord Types Major Key
- Major Triads: I, IV, VI
- Minor Triads: II, III, VI
- Diminished Triad: III
- Dominant Seventh Chord: V7
- Major Seventh Chord: I7, IV7
- Minor Seventh Chord: II7, III7, VI7
- Half Diminished Seventh Chord: VII7
Chord Types Harmonic Minor Key
- Minor Triads: I, IV
- Major Triads: V, VII
- Diminished Triad: II, VII
- Augmented Triad: III
- Dominant Seventh Chord: V7
- Minor Seventh Chord: I7, IV7
- Major Seventh Chord: VI7
- Half Diminished Seventh Chord: II7
- Diminished Seventh Chord: VII7
Inversions
Triad:
- Root Position: C-E-G
- First Inversion: E-G-C
- Second Inversion: G-C-E
Seventh Chord:
- Root Position: G-B-D-F
- First Inversion: B-D-F-G
- Second Inversion: D-F-G-B
- Third Inversion: F-G-B-D | 
