Understanding Triads in Music Theory: A Complete Guide

Voice leading transforms basic triads into beautiful 4-voice harmonies by treating chords as moving melodic lines rather than static figures. The four fundamental principles are: (1) Maintain common notes between chords as pivot points; (2) Double the fundamental most frequently, then the fifth, and finally the third; (3) Never connect two chords with the same disposition to avoid parallel fifths and octaves; (4) Use inversions strategically, with first inversion allowing more freedom and second inversion requiring careful bass movement. These principles apply across all musical contexts, from vocal ensembles to instruments like strings and keyboards.

This section covers the foundational principles of voice leading in classical harmony. It explains why parallel fifths are prohibited in classical music, clarifying that they are actually results of incorrect voice leading rather than the cause of problems. The content details how four-part harmony (SATB) requires strategic distribution of notes among voices, treating it like a puzzle. The key principle is that when the bass moves down, other voices should move up to maintain balance, and vice versa. This creates natural, smooth voice connections that are essential for proper harmonic progression.

Voice leading principles guide how harmony parts move between chords. In SATB format (soprano-alto-tenor-baritone), harmony parts maintain common tones across chord changes for smooth transitions. For example, in C-G-Am-F progression, the soprano line might go E-G-C-C to take advantage of common tones between chords. When harmonizing above a melody, you may need to skip notes to avoid creating perfect intervals that occur naturally when following the melody closely. These principles ensure harmonies sound connected and natural rather than jarring.

Voice leading principles in four-part harmony include: (1) doubling the tonic note of each chord, (2) maintaining common notes between consecutive chords to create smooth transitions, (3) applying the 'law of least effort' by moving voices to the closest possible notes rather than making large leaps, and (4) avoiding intervals larger than an octave between voice parts to maintain harmonic balance. These principles ensure smooth, natural-sounding harmonic progressions that are easier to perform and more aesthetically pleasing.

In four-part voice leading, chord construction follows specific rules: use the middle range of each voice for balance, double the root in root-position triads but avoid doubling tendency tones (leading tones and sevenths); every chord needs a root and third to define its quality, though fifths can occasionally be omitted; maintain no more than an octave between upper voices and avoid voice crossing, while distinguishing between close position (no space between chord tones) and open position (space exists between chord tones).

Cadences describe how chords lead to or resolve to each other. The authentic cadence (V-I) is the strongest resolution in Western music. The 1-5-6-4 progression uniquely lacks this resolution, creating a sense of continuous motion. It contains three key cadences: the half cadence (I-V), the deceptive cadence (V-vi) that defies expectations, and the plagal cadence (IV-I) that completes the loop. These cadences work together to create the progression's distinctive feeling of unresolved tension and forward motion.

Roman numeral analysis provides a systematic framework for understanding musical harmony through five interconnected steps: (1) Determine the key from the key signature, considering both major and minor possibilities; (2) Construct triads by stacking thirds above each scale degree; (3) Assign Roman numeral labels based on scale position (I, II, III, IV, V, VI, VII); (4) Identify extended chords by continuing to stack thirds beyond the basic triad; (5) Determine chord inversions by identifying which note occupies the bass position (root position = a, first inversion = b, second inversion = c, third inversion = d). This methodology enables analysts to decode harmonic structure, identify key centers, recognize chord progressions, and understand how composers create harmonic motion and resolution within a musical piece.

A chord progression is a chain of chords played in a specific order with rhythm. Music theory provides tendencies, not rigid rules, for building progressions. Each chord has a scale degree number. The fifth degree (dominant) creates tension that resolves to the first degree (home chord). Cadences function as musical punctuation: authentic cadence (5-1) is the most conclusive, acting like a full stop; half cadence (ending on 5) creates tension like a question mark; deceptive cadence (5-6) subverts expectations for surprise; plagal cadence (4-1) provides softer resolution. These tools create questions, answers, and emotional contour in musical phrases.

The video demonstrates cadences—the harmonic progressions that signal musical resolution and closure. Cadences mark the ending of musical phrases and create a sense of completion or anticipation for what follows. The mix shows how different types of cadences (authentic, plagal, half-cadences) serve different functions in musical structure. Understanding cadences is fundamental to music theory and helps listeners perceive the architectural framework of musical compositions.

Cadences are harmonic progressions that create a sense of resolution or completion. The plagal cadence moves from IV to I (e.g., F to C in C major), creating a gentle resolution. The authentic cadence moves from V to I (e.g., G to C in C major), creating strong finality. The compound cadence combines both: IV to V to I (e.g., F to G to C). These cadences work identically in both major and minor keys, though the specific chords involved will be minor triads in minor keys. The plagal cadence is also known as the 'amen cadence' due to its common use in sacred music.

Three fundamental non-chord tone types involve stepwise motion. Passing tones connect chord tones a third apart with linear motion. Neighbor tones embellish single chord tones with away-and-back gestures. Double passing tones connect chord tones a fourth apart with two consecutive non-chord tones. All require careful treatment as they are typically dissonant and classified by their melodic relation to surrounding tones.

Non-chord tones are pitches that do not belong to the primary harmony at a given moment, creating harmonic tension and interest; they are classified based on how they are approached and resolved, with eight main types including passing tones (approached and resolved by step in same direction), neighbor tones (approached by step but resolved in opposite direction), appoggiaturas (approached by leap and resolved by step), escape tones (approached by step and resolved by leap), double neighbors (combining upper and lower neighbors with a leap), suspensions (approached by common tone and resolved down by step), retardations (approached by common tone and resolved up by step), and anticipations (approached by step and resolved by common tone).

Non-chord tones (passing tones and neighbour tones) can significantly enhance plain harmony by adding melodic interest; passing tones should be inserted between melodic thirds where they approach and leave by step, while neighbour tones work best with repeated notes by moving up and back or down and back; however, composers must balance embellishment with harmonic clarity, as excessive use can create congestion or dissonance, and special care is needed when enriching chords like V to V7 to ensure proper resolution rules are maintained.

Non-chord tones are notes that do not belong to the current chord but serve important melodic functions; they include passing tones (stepwise movement between chord tones), neighbor tones (step away then back), appoggiatura (leap then step), escape tone (step then leap), anticipation (early arrival), suspension (held note resolving down), and retardation (held note resolving up). These tones add character and emotional depth to melodies when used intentionally in composition or improvisation.

Non-chord tones (NCTs) are pitches that do not belong to the current chord and must be prepared and resolved according to specific rules to create musical tension and release; the main types include passing tones (approached and resolved by step in the same direction), neighbor tones (approached by step and resolved by step in the opposite direction), suspensions (prepared by common tone and resolved down by step), retardations (prepared by common tone and resolved up by step), appoggiaturas (approached by leap and resolved by step in the opposite direction), escape tones (approached by step and resolved by leap in the opposite direction), anticipations (prepared by step or leap and resolved by common tone), pedal points (prepared and resolved by common tone), and neighbor groups (both upper and lower neighbors together); each type has specific placement rules, typically occurring on weak beats except suspensions and retardations which occur on strong beats, and they must follow the two fundamental rules: only one NCT per chord and at least one moment where the complete chord sounds without interference.

In music theory for songwriters, borrowed chords are chords taken from the parallel minor key (sharing the same tonic) that add harmonic color to major key compositions, such as the flat third major chord (C major in A major) and flat sixth/fifth major chords (F major and G major in A major); secondary dominant chords are dominant seventh chords that lead to other chords in the key (like F#7 leading to Bm or C#7 leading to F#m), creating tension and resolution that enhances songwriting by providing common progressions like I to flat three major to four major to four minor, which features the powerful leading tone effect where the third of the borrowed chord resolves up a half step to the fourth chord.

This section establishes the theoretical foundation for chromatic harmony. Diatonic music restricts itself to the notes of a specific major or minor scale, while chromatic music makes all 12 notes available, representing the highest resolution of pitch organization. A dominant chord is defined as a major triad topped with a minor seventh, creating instability through the tritone between third and seventh. Secondary dominants are created by transforming any diatonic chord into a dominant chord (adding a seventh), creating strong expectation that the next chord will be the one a fifth below. Using the cycle of fifths, every chord can be transformed to create the next secondary dominant, creating a solar system-like structure where each degree has a 'moon' orbiting around it.

Advanced chord progressions use sophisticated harmonic devices to create interest. Secondary dominant chords temporarily function as the dominant of a different key, creating tension that resolves elsewhere. Borrowed chords, taken from parallel minor keys, add color and were commonly used by The Beatles. Chromatic mediant modulation involves borrowing chords from keys a third away, creating sophisticated harmonic movement. These techniques allow songwriters to move beyond the standard one-four-five-six progression while maintaining musical coherence.

To modulate to a parallel minor key, use a dominant seventh chord that belongs to the new key. For example, to modulate from F major to F minor, use D7 (the dominant of G) which resolves to G major, then use Eb7 (the dominant of F minor) to resolve to F minor. The modulation point is where the dominant seventh of the new key appears. A dominant seventh chord can serve as a bridge between keys. To modulate, create a dominant seventh chord that belongs to the new key. For example, to modulate from F major to G minor, use D7 (the dominant of G) which resolves to G minor. A backdoor dominant can be used for modulation. For example, to modulate from G minor to F minor, use E7 (the dominant of A) which resolves to A major, then use Eb7 (the dominant of F minor) to resolve to F minor. Borrowed chords are chords taken from parallel keys or related keys. For example, in G minor, A major (the major of the parallel major) can be borrowed.