Figured Bass Symbols

Why This Matters

Figured bass is the shorthand language that unlocks how chords actually function in tonal music. When you see a Roman numeral with figures beneath it, you're not just identifying a chord—you're understanding which note is in the bass, how the voices will move, and what harmonic tension exists. These symbols appear constantly in AP Music Theory analysis, from simple chorale harmonizations to complex chromatic passages.

You're being tested on your ability to read these symbols quickly, realize them correctly, and understand their voice-leading implications. Don't just memorize that "6/4" means second inversion—know why a cadential $6/4$ creates tension, how seventh chord inversions resolve, and which chromatic chords signal modulation. Master the underlying logic, and figured bass becomes intuitive rather than intimidating.

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Triad Inversions: Building Blocks of Voice Leading

Triad inversions determine which chord tone sits in the bass, fundamentally shaping how smooth or angular your bass line sounds. The figures tell you the intervals above the bass note, not above the root.

Root Position (5/3 or no figure)

• Root in the bass—the most stable voicing, often used at phrase beginnings and endings
• Implied when no figures appear; the "5/3" is typically omitted in notation
• Creates harmonic weight and establishes clear tonal centers in progressions

First Inversion (6 or 6/3)

• Third in the bass—produces a lighter, more mobile sound than root position
• Notated as "6" because the root sits a sixth above the bass (the "3" is usually omitted)
• Essential for smooth bass lines, allowing stepwise motion between chords

Second Inversion (6/4)

• Fifth in the bass—the least stable triad voicing, requiring special treatment
• Always notated as "6/4" to flag its unstable character
• Three main uses: cadential, passing, and pedal—know which context applies

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Seventh Chord Inversions: Tracking the Dissonance

Seventh chords add a dissonant interval that must resolve, and the figures tell you exactly where that dissonance sits relative to the bass. Each inversion has a characteristic resolution pattern.

Root Position Seventh (7)

• Root in the bass with seventh above—the full stack of 7/5/3 is implied
• Notated simply as "7" with other intervals assumed
• Seventh resolves down by step, typically while the chord moves to its resolution

First Inversion Seventh (6/5)

• Third in the bass—the seventh now sits a fifth above the bass note
• Notated as "6/5" to show both the sixth (root) and fifth (seventh) above bass
• Common in sequences and provides smooth voice leading to the next chord

Second Inversion Seventh (4/3)

• Fifth in the bass—the seventh sits a third above the bass note
• Notated as "4/3" indicating the root (fourth) and seventh (third) above bass
• Frequently appears in dominant function, especially approaching cadences

Third Inversion Seventh (4/2 or 2)

• Seventh in the bass—the most unstable inversion, demanding immediate resolution
• Notated as "4/2" or simply "2" to indicate the root a second above the bass
• Bass must resolve down by step, making this inversion highly directional

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Chromatic Chords: Signaling Harmonic Intensification

Chromatic harmonies use altered scale degrees to create heightened tension and directional pull. These chords often signal approaching cadences or modulations.

Diminished Seventh Chord (°7)

• Diminished triad plus diminished seventh—all intervals are minor thirds
• Notated with "°7" (or "o7") to indicate the fully diminished quality
• Symmetrical structure allows enharmonic reinterpretation, making it a powerful modulatory tool

Neapolitan Sixth (N6 or ♭II6)

• Major triad built on lowered scale degree 2, always in first inversion
• Notated as "N6" and functions as a pre-dominant chord
• Resolves to V (often through a cadential 6/4), adding rich harmonic color

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Augmented Sixth Chords: The Dominant Approach

Augmented sixth chords share a defining interval—the augmented sixth—that expands outward to an octave on the dominant. The three types differ only in their upper voices.

Italian Augmented Sixth (It+6)

• Three notes only: ♭6, 1, and #4 (the augmented sixth interval plus the tonic)
• Notated as "It+6" and is the simplest augmented sixth chord
• Resolves to V with the outer voices expanding to an octave on scale degree 5

French Augmented Sixth (Fr+6)

• Four notes: adds scale degree 2 to the Italian structure
• Notated as "Fr+6" and contains two tritones, creating extra tension
• Distinctive whole-tone flavor from its symmetrical interval structure

German Augmented Sixth (Ger+6)

• Four notes: adds ♭3 (or #2) to the Italian structure
• Notated as "Ger+6" and sounds like a dominant seventh chord
• Resolves to cadential 6/4 to avoid parallel fifths, then to V

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Quick Reference Table

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Self-Check Questions

1. Which two seventh chord inversions place the dissonant seventh closest to the bass, and how does this affect their resolution?

2. A chord is labeled "6/4" in your analysis. What three contexts might justify this unstable voicing, and which is most common at cadences?

3. Compare the Italian, French, and German augmented sixth chords: what note distinguishes each, and why does the German require special voice-leading treatment?

4. You see a "°7" chord on the leading tone. How might you reinterpret this chord enharmonically to modulate to a distant key?

5. An FRQ asks you to harmonize a bass line that descends by step from scale degree 1 to scale degree 5. Which inversions would create the smoothest voice leading, and why?