Interrupted Cadence

An interrupted cadence (also called a deceptive cadence) occurs when a dominant chord (V) does not resolve to the expected tonic chord (I) but instead moves to another chord, commonly the submediant (vi). This creates a sense of surprise or a musical question mark, making the music sound as if it should continue rather than end.

The movement is written as V–vi. For example, in C major, the progression would be G major (V) to A minor (vi).

Non-Harmonic Tones

Non-harmonic tones (also called non-chord tones) are notes that do not belong to the chord currently being played. They decorate the melody by adding interest, tension, or movement, and usually resolve to a note that is part of the chord.

Types of Non-Harmonic Tones

Worked Example: In C major, if you have a C-E-G chord and want to connect C to E smoothly, you would use a passing tone D between them.

Modulation

Modulation is the process of changing from one key to another within a composition. It introduces variation, keeps the listener engaged, and expresses different moods.

Types of Modulation

Monophonic modulation occurs when a melody changes key without chords—through accidentals and a clear shift toward the notes of the new key. The change usually occurs between closely related keys.

Common modulation (pivot modulation) uses a chord shared by both keys (a pivot chord) as a bridge between them. This ensures a smooth change in tonality.

Principles of Modulation

1. Establish the home key – Determine the original key
2. Choose a related key – Modulate to a closely related key (dominant, subdominant, or relative minor)
3. Find pivot note or chord – Identify a note/chord belonging to both keys
4. Establish the dominant of the new key – Use the dominant chord with an accidental on the leading tone
5. Confirm with cadence – Use a perfect cadence (V–I) to prove the new key
6. Continue with common progression – Move to subdominant or supertonic to prepare for another cadence

Worked Example: Modulating from G major to D major (dominant):

• Pivot chords shared: G major, B minor, D major, E minor
• The dominant of the new key (D major) is A major
• Confirm with perfect cadence: A major → D major

Seventh Chords

A seventh chord consists of four notes: root, third, fifth, and seventh. Two important seventh chords at this level are:

Dominant Seventh Chord (V⁷)

• Root is the dominant (fifth degree) of the scale
• In major keys: major triad + minor seventh
• In minor keys: uses harmonic minor (raised seventh) for strong resolution

Worked Example: In C major, the dominant seventh chord is G-B-D-F (G⁷).

Supertonic Seventh Chord (ii⁷)

• Root is the supertonic (second degree) of the scale
• In major keys: minor triad + minor seventh (ii⁷)
• In minor keys: diminished triad + minor seventh (iiø⁷)

Worked Example: In C major, the supertonic seventh chord is D-F-A-C (ii⁷). In A minor, it is B-D-F-A (iiø⁷).

Figured Bass for Seventh Chords

Seventh chords have four positions:

Worked Example: The dominant seventh chord G-B-D-F in C major:

• Root position: G (bass) → V⁷
• First inversion: B (bass) → V⁶⁄₅
• Second inversion: D (bass) → V⁴⁄₃
• Third inversion: F (bass) → V⁴⁄₂

Application in Harmony

When using seventh chords:

1. Prepare the seventh – The seventh note must be prepared (usually by holding the same note)
2. Resolve the seventh – The seventh resolves downward by step (except in retardation, which resolves upward)
3. Treat the tritone – In dominant seventh, the tritone (between third and seventh) resolves: third up, seventh down

Worked Example: In the progression V⁷–I, the seventh (F) resolves down to E (the third of the tonic chord in C major: G-B-D-F → C-E-G-C).

Harmonising a Melody with Seventh Chords

Follow these steps:

1. Identify the key of the melody
2. Identify possible cadences
3. Indicate possible chords (include V⁷ and ii⁷)
4. Write the bass line following the chords
5. Add tenor and alto parts
6. Add embellishments (non-harmonic tones)
7. Play or sing to verify

In Tanzania, understanding modulation and non-harmonic tones helps musicians arrange music for local instruments like the ngoma or guitar for church choirs and wedding bands. For example, when arranging a worship song in Dar es Salaam, a musician might use an interrupted cadence (V–vi) to create emotional tension before resolving to the tonic, making the congregation feel the music is leading them to a meaningful climax—just as the textbook describes how composers use these techniques to keep audiences engaged.