Getting Started
Music is more than a sequence of pitches and rhythms; it is a language with its own grammar and logic. This chapter explores the fundamental cause-and-effect relationships that govern how chords connect to one another. By understanding these principles, we can move from simply identifying chords to explaining why they progress in a way that sounds coherent and purposeful.
What You Should Be able to Do
Identify the function of a given chord within a key.
Provide a Roman numeral analysis for a common diatonic chord progression.
Explain how harmonic function creates musical tension and release.
Differentiate between chords that establish stability and those that create a need for resolution.
Construct a grammatically correct chord progression using tonic, predominant, and dominant functions.
Key Concepts & Analysis
The primary driver of harmonic causation is functional harmony. This is a system where each chord in a key is assigned a role or "function" based on its relationship to the tonic, the chord built on the first scale degree (^1). These functions create a predictable flow of tension and release, forming the backbone of tonal music. The three main functions are Tonic, Dominant, and Predominant.
Functions & Allowable Motions
A chord's function dictates where it is likely to move next, creating a logical path through a musical phrase. The standard model of harmonic progression is a journey away from and back to stability.
Tonic (T): The function of rest and stability. Tonic is the home base of a key. The progression begins and ends here. Chords with tonic function are I (or i in minor) and, to a lesser extent, vi (or VI).
Predominant (PD): The function of transition. Predominant chords prepare the arrival of the dominant, moving the harmony away from the stability of the tonic. Chords with predominant function include IV (or iv) and ii (or ii°).
Dominant (D): The function of tension. Dominant chords create a strong expectation for resolution back to the tonic. This is the most unstable and forward-driving function. Chords with dominant function are V and vii°.
The most common and logical path for these functions is T → PD → D → T. While it is possible to skip the predominant (T → D → T), moving backward (e.g., D → PD) is ungrammatical and rare in common practice music.
Common Progressions
These functional motions result in a set of highly common and recognizable chord progressions. Roman numerals are used to label chords by the scale degree of their root, while their quality (major, minor, diminished) is shown with uppercase, lowercase, and the diminished symbol (°).
The Complete Progression: I–IV–V–I; i–ii°6–V–i
Skipping the Predominant: I–V–I; i–V–i
Using the Supertonic: I–ii–V–I; i–ii°–V–i
Using the Submediant as a Tonic Prolongation: I–vi–IV–V–I; i–VI–iv–V–i
Cadence Implications
A cadence is a melodic and harmonic endpoint of a phrase, analogous to punctuation in language. The type of cadence is determined by the final two chords, whose functions create varying degrees of finality.
Authentic Cadence (AC): A cadence ending on the tonic chord, preceded by a dominant-function chord (V or vii°). This provides a strong sense of closure. The strongest type is the Perfect Authentic Cadence (PAC), where V moves to I, both chords are in root position, and the tonic is in the highest voice of the I chord.
Half Cadence (HC): A cadence ending on the dominant (V) chord. This creates a feeling of pause or expectation, leaving the phrase unresolved and requiring continuation.
Data & Organization Tools
This table organizes the diatonic triads for major and minor keys, showing their quality, Roman numeral, and typical harmonic function. Understanding these relationships is essential for analyzing and creating logical progressions.
| Key | Scale Degree | Triad Quality | Roman Numeral | Function |
|---|---|---|---|---|
| Major | ^1 | Major | I | Tonic (T) |
| ^2 | minor | ii | Predominant (PD) | |
| ^3 | minor | iii | (Tonic/Dominant) | |
| ^4 | Major | IV | Predominant (PD) | |
| ^5 | Major | V | Dominant (D) | |
| ^6 | minor | vi | Tonic (T) | |
| ^7 | diminished | vii° | Dominant (D) | |
| Minor | ^1 | minor | i | Tonic (T) |
| ^2 | diminished | ii° | Predominant (PD) | |
| ^3 | Major | III | (Tonic) | |
| ^4 | minor | iv | Predominant (PD) | |
| ^5 | Major | V | Dominant (D) | |
| ^6 | Major | VI | (Predominant) | |
| ^7 | diminished | vii° | Dominant (D) |
Note: In minor keys, the leading tone (^7) is raised to create a major V and diminished vii° chord, strengthening the dominant function.
Evidence Bank
Tonic Function: The harmonic role of providing stability and a sense of "home." The I (or i) chord is the primary tonic.
Dominant Function: The harmonic role of creating tension that demands resolution to the tonic. The V chord is the primary dominant.
Predominant Function: The harmonic role of preparing the dominant, acting as a transition away from tonic. The IV and ii chords are the primary predominants.
Roman Numeral Analysis: A method of labeling chords that indicates the scale degree of the root and the chord's quality. This is the primary tool for analyzing functional harmony.
Chord Quality: The sound of a chord based on its interval structure (major, minor, diminished, augmented). Quality is determined by the scale but is secondary to function.
Authentic Cadence: The strongest concluding gesture in tonal music, consisting of a D–T (V–I) harmonic progression.
Half Cadence: An inconclusive gesture that ends on a V chord, creating a pause and an expectation to continue.
Harmonic Progression: A sequence of chords. In functional harmony, progressions are not random but follow a logical grammar (T–PD–D–T).
Skill Snapshots
Functional
I–IV–V–I: This is the archetypal progression. It moves from tonic stability (I), through a predominant preparation (IV), to maximum tension (V), before resolving back to tonic (I).
i–VI–iv–V–i: In minor, the VI chord can substitute for the tonic before moving to the predominant (iv), creating a smoother departure from the home key area.
I–V6/5–I6: This progression uses an inverted dominant seventh chord. The inversion softens the dominant's drive slightly but still follows the essential T–D–T motion.
Voice-Leading
Leading-Tone Resolution → Strong Dominant: The leading tone (^7) is only a half step below the tonic (^1). Its strong melodic tendency to resolve upward is a primary cause of the V chord's powerful pull to the I chord.
Chordal Seventh Resolution → Forward Motion: The seventh of a dominant seventh chord (the fourth scale degree, ^4) is dissonant and has a strong tendency to resolve down by step to the third of the tonic chord (^3). This adds another layer of causal force to the D–T progression.
Root Position V–I → Finality: Using both the V and I chords in root position at a cadence creates the strongest possible bass motion (a leap of a P4 or P5), which reinforces the sense of finality.
Form
Baseline Phrase: A musical idea ending with a cadence. A simple phrase might use the progression I–ii6–V–I, ending with an authentic cadence for a sense of completion.
Contrast (HC vs. AC): A phrase ending with I–IV–V (a half cadence) feels unfinished. A subsequent phrase that answers it by ending with I–IV–V–I (an authentic cadence) provides the resolution the first phrase lacked.
Continuity: The unresolved nature of a half cadence causes the listener to expect more music, creating continuity and linking phrases together into larger formal units.
Common Misconceptions & Clarifications
Misconception: Every progression must include all three functions (T, PD, D).
- Clarification: The T–D–T progression is extremely common. The predominant function serves to expand the phrase but is not strictly required.
Misconception: A chord's quality is the same as its function.
- Clarification: Function describes a chord's role in a key, while quality describes its internal sound. In C major, both I (C major) and IV (F major) are major chords, but they have different functions (Tonic vs. Predominant).
Misconception: The iii chord is a common and important chord.
- Clarification: While diatonic, the iii chord has an ambiguous function and is used far less frequently than I, IV, and V. It can sometimes substitute for a tonic or precede a predominant.
Misconception: Harmonic motion is always forward (T→PD→D).
- Clarification: While forward motion is the norm, chords can move within a functional family. For example, a tonic I chord can move to another tonic-function chord like vi before the progression continues to the predominant area (e.g., I–vi–IV).
Summary
The principles of causation in music fundamentals are rooted in the system of functional harmony. This system assigns a specific role—Tonic, Predominant, or Dominant—to each chord within a key, based on its relationship to the tonal center. These functions create a logical and predictable grammar of chord progression, most commonly T → PD → D → T, which generates musical tension and release. By analyzing music with Roman numerals, we can identify these functions and understand how pitch and harmony work together to create coherent phrases, punctuated by cadences. This underlying logic is what transforms a simple collection of chords into a compelling musical narrative.