Triads are the building blocks of harmony in Western music. These three-note chords consist of a root, third, and fifth, stacked in thirds. They come in four main types: major, minor, diminished, and augmented, each with a unique sound and function.

Triads can be inverted by changing the bass note, altering their stability and voice leading possibilities. Understanding triads and their inversions is crucial for analyzing chord progressions, creating smooth bass lines, and composing effective harmonies in various musical styles.

Definition of triads

• Triads are the most basic type of chord in Western tonal music consisting of three notes stacked in thirds
• The three notes of a triad are called the root, third, and fifth which together form the foundation of harmony
• Triads can be built on any scale degree and the quality of the triad depends on the intervals between the notes

Root position triads

• Root position triads have the root note as the lowest pitch with the third and fifth stacked above
• In root position, the triad is in its most stable arrangement with the tonic note in the bass
• The intervals in a root position triad are a third and a fifth above the bass note (root)

Inverted triads

• Inverted triads have either the third or the fifth as the lowest note instead of the root
• Inverting a triad changes the bass note and the intervals above it while preserving the core pitches
• Inverted triads are less stable than root position triads but provide more melodic and harmonic variety

Types of triads

• There are four main types of triads in tonal music each with a distinct sound and function
• The quality of a triad depends on the size of the intervals between the root, third, and fifth
• Different triad qualities can be used to create different moods and harmonic colors in a piece

Major triads

• Major triads consist of a major third and a perfect fifth above the root (C-E-G)
• The major third gives the triad a bright, happy, and stable sound suitable for resolution
• Major triads are found on the I, IV, and V scale degrees in major keys

Minor triads

• Minor triads consist of a minor third and a perfect fifth above the root (C-Eb-G)
• The minor third gives the triad a darker, sadder, and more unstable sound compared to major
• Minor triads are found on the ii, iii, and vi scale degrees in major keys

Diminished triads

• Diminished triads consist of a minor third and a diminished fifth above the root (C-Eb-Gb)
• The diminished fifth is a dissonant interval that gives the triad a tense, unresolved sound
• Diminished triads have a strong tendency to resolve to a more stable chord and are found on the vii° in major and minor keys

Augmented triads

• Augmented triads consist of a major third and an augmented fifth above the root (C-E-G#)
• The augmented fifth is a dissonant interval that gives the triad an ambiguous, unstable sound
• Augmented triads are symmetrical and can function as altered chords or to modulate to a distant key

Triad inversions

• Triads can be inverted by moving the lowest note up an octave resulting in a different bass note and intervallic arrangement
• Inversions are labeled by the scale degree of the bass note and change the harmonic function and voice leading of the triad
• Composers use inversions to create smoother bass lines, avoid parallel fifths and octaves, and add variety to chord progressions

Root position

• In root position (5/3), the root is the bass note with the third and fifth stacked above
• Root position triads are the most stable and conclusive sounding especially when the root is doubled
• Root position is commonly used for cadences, phrase endings, and strong harmonic arrivals

First inversion

• In first inversion (6/3), the third is the bass note with the root and fifth above
• First inversion triads have a lighter, less final sound than root position and are useful for connecting chords in stepwise motion
• The intervals above the bass in first inversion are a third and a sixth

Second inversion

• In second inversion (6/4), the fifth is the bass note with the root and third above
• Second inversion triads are the least stable with a fourth above the bass that wants to resolve down by step
• The intervals above the bass in second inversion are a fourth and a sixth
• Second inversion is often used as a passing or cadential 6/4 chord to embellish and lead to a stronger root position chord

Figured bass notation

• Figured bass is a shorthand notation used in the Baroque era to indicate chord inversions and intervals above the bass
• Numbers are written below the bass note to show the size of the intervals stacked above (not counting the bass)
• Accidentals can be used to raise or lower certain intervals and further specify the chord quality

Intervals above the bass

• The most common figured bass symbols are:
  • 5/3 - root position triad (third and fifth above the bass)
  • 6/3 - first inversion triad (third and sixth above the bass)
  • 6/4 - second inversion triad (fourth and sixth above the bass)
• Other intervals can be indicated like 7 for a seventh chord, 4-3 for a suspension, or 6/5 for a cadential 6/4 chord

Shorthand notation

• Figured bass symbols can be abbreviated for quicker reading and writing
• Root position triads are often left unmarked since they are the most common
• First inversion triads can be reduced to just 6 and second inversion to just 4 or 2
• Dashes are used to extend a figure across multiple bass notes and 0 indicates a diminished interval

Identifying triads

• Being able to quickly identify and label triads is an essential skill for analyzing and performing tonal music
• Triads can be identified by the scale degree of their root, their quality (major, minor, diminished, augmented), and their inversion
• Multiple ways of naming the same triad enrich our understanding of its musical context and function

By root note

• Triads are named after the scale degree on which they are built (tonic, supertonic, mediant, etc.)
• In major keys, the I, IV and V are major triads, the ii, iii, and vi are minor, and the vii° is diminished
• In minor keys, the i and iv are minor, the III, V and VI are major, the ii° and vii° are diminished

By quality

• The quality of a triad depends on the intervals between the root, third, and fifth
• Major triads have a major third and perfect fifth, minor triads have a minor third and perfect fifth
• Diminished triads have a minor third and diminished fifth, augmented triads have a major third and augmented fifth

By inversion

• Labeling triads by inversion specifies which note is in the bass and how the upper voices are arranged
• Inversions can be identified by the intervals they form above the bass (5/3, 6/3, 6/4) or their figured bass symbols
• Hearing and labeling inversions is important for understanding how triads are used in chord progressions and voice leading

Triad progressions

• Triads are rarely used in isolation but rather in succession to create harmonic progressions
• Common triad progressions in major and minor keys follow patterns of root movement by fourth, fifth, third or step
• Chords within a progression are labeled with Roman numerals to show their scale degree function

Common progressions

• I-IV-V-I (authentic cadence) and I-V-I (half cadence) are common progressions that establish the tonic key
• ii-V-I (turnaround) and I-vi-ii-V (circle of fifths) are used to extend phrases and create forward momentum
• I-iii-IV-I and I-vi-IV-V (plagal cadence) are common in popular music for their simple, consonant sound

Voice leading considerations

• Triad progressions should be connected with smooth, efficient voice leading between the upper notes
• Common tones between chords should be held in the same voice while other voices move to the nearest chord tone
• Parallel fifths and octaves between outer voices should be avoided by using contrary or oblique motion
• Chords in first or second inversion are useful for creating stepwise bass lines and smoother voice leading

Triads in musical context

• Beyond their basic structure and function, triads take on expressive meaning based on how they are used in real music
• The same triad can sound and function differently depending on its melodic, harmonic, rhythmic, and timbral context
• Comparing the use of triads vs more complex chords like seventh chords reveals different musical styles and textures

Triads in melody

• Triads can be used melodically as broken chords or arpeggios to outline the harmony
• Triad tones are often used as embellishing tones (passing tones, neighbor tones, suspensions) to decorate a melody
• The top note of the triad is often prominent as the melody note, especially when it is the third or seventh of the chord

Triads in harmony

• Triads form the basic building blocks of harmony in homophonic and polyphonic textures
• Chord progressions, cadences, and modulations are created by combining triads in a particular key
• The same triad can function differently based on its position in the phrase and relationship to other chords (tonic, dominant, pre-dominant)

Triads vs seventh chords

• Triads are more stable, consonant and simple sounding compared to seventh chords which add an extra note and more dissonance
• Seventh chords (both diatonic and secondary dominants) became increasingly common in the Romantic era for their richer, more complex sound
• Jazz and other modern styles use extended tertian harmonies beyond triads and seventh chords (9th, 11th, 13th)
• Understanding how triads work is the foundation for learning more advanced harmonies and chord progressions