Harmony and tonality: chords, cadences, functional harmony, diatonic and chromatic harmony, modulation, keys and modes, and dissonance and consonance.

What this dot point is asking

Harmony and tonality are core elements of the Component 1 appraising toolkit, examined in the Section A listening questions and underpinning the Section B essay. AQA wants you to describe chords and cadences, explain functional harmony, distinguish diatonic from chromatic harmony, recognise modulation, keys and modes, and use consonance and dissonance precisely when analysing both familiar set works and unfamiliar extracts.

Keys, modes and tonality

A key is defined by its tonic and the scale built on it. The major scale has the pattern tone, tone, semitone, tone, tone, tone, semitone; the natural minor lowers the third, sixth and seventh degrees. In practice the minor mode is flexible: the harmonic minor raises the seventh to create a leading note (so the dominant chord becomes major and pulls strongly to the tonic), while the melodic minor raises the sixth and seventh ascending and reverts to the natural minor descending to smooth the awkward augmented second. Recognising the raised leading note is often the quickest way to confirm a minor key by ear. Related keys share most of their notes: a key and its relative (for example C major and A minor) share a key signature, while a key and its dominant differ by a single sharp or flat, which is why so much tonal music gravitates to the dominant.

Chords and cadences

Chords are built by stacking thirds on a scale degree. A triad has a root, third and fifth; adding a further third gives a seventh chord. The most important seventh in tonal music is the dominant seventh, $V^7$, whose dissonant tritone between the third and seventh resolves crisply onto the tonic, which is why it sharpens a perfect cadence. Inversions change which chord member sits in the bass: a first inversion ($Vb$ or $V^6$) has the third in the bass and softens the harmony, while the cadential second inversion of the tonic ($Ic$) delays the dominant and is a hallmark of Classical cadences. Knowing inversions lets you describe the bass line, not just the chord names, and bass movement is a reliable marker AQA credits.

Diatonic, chromatic and modulation

Diatonic harmony uses only the notes of the prevailing key. Chromatic harmony adds notes from outside the key for colour and tension. Two named chromatic chords appear repeatedly in the set works. A secondary dominant is the dominant of a chord other than the tonic, written for example as $V/V$ (the dominant of the dominant), and it tonicises that chord for a moment, brightening the harmony before a modulation. The augmented sixth chords (Italian, French and German) contain an interval of an augmented sixth that expands outward onto the dominant, giving a strong, dark approach to a cadence in both Baroque and Romantic music. Modulation is a move from one key to another, confirmed by a cadence in the new key; the commonest journeys are to the dominant, the relative major or minor, and the subdominant. Composers usually modulate through a pivot chord that belongs to both keys, which is why the change can sound smooth rather than abrupt.

Consonance and dissonance

Consonant intervals (the perfect unison, octave, fourth and fifth, and the major and minor thirds and sixths) sound stable and restful; dissonant ones (seconds, sevenths and the tritone) sound tense and typically resolve onto consonance. The dissonances examiners most want named are the suspension (a note held over from the previous chord that clashes, then resolves downward by step, labelled by its intervals such as a $4$ to $3$ suspension), the passing note (a stepwise non-harmony note between two chord notes) and the appoggiatura (an accented dissonance that leans onto the beat before resolving). Pedal points, a sustained note (usually tonic or dominant) under changing harmony, are another examinable device that builds tension or stability. In every case the mark comes from naming the device and saying how it resolves.