The tritone interval formed between the third and seventh of a seventh chord (e.g., B-F in a G7 chord) creates dissonance that demands resolution. The tritone resolves by inward motion: the upper note steps down to the third of the target chord, the lower note steps up to the seventh. This resolution requirement shapes voice leading in dominant seventh and secondary dominant chords. Proper tritone resolution creates strong harmonic closure and defines the function of the seventh chord.
Play tritones on an instrument and feel the tension and resolution when voices move inward. Then write V7-I progressions where you resolve the tritone in multiple voicings to internalize the principle.
From your prerequisite in seventh chords, you know how to build dominant seventh chords and identify their components: root, major third, perfect fifth, and minor seventh. From harmonic function basics, you know that the dominant chord creates tension that demands resolution to tonic. Tritone voice leading explains why the dominant seventh creates such powerful tension and how it resolves — through the specific interval mechanics of the tritone, the most unstable interval in tonal music.
The tritone is the interval between the third and the seventh of a dominant seventh chord. In G7 (G-B-D-F), the tritone spans B to F — an augmented fourth (or diminished fifth, depending on how you spell it), exactly six half steps, bisecting the octave. This interval is the most dissonant in tonal music because it sits at the farthest possible point from consonance: it is neither a simple ratio like the perfect fifth (3:2) nor close enough to one to feel nearly consonant. The tritone's instability creates a strong perceptual demand for resolution — the ear wants it to move somewhere more stable.
The resolution pattern is inward contrary motion: the two notes of the tritone move toward each other by half step. In G7 resolving to C major, B (the leading tone, the lower note of the tritone as an augmented fourth) rises by half step to C, while F (the chordal seventh, the upper note) falls by half step to E. The tritone contracts from an augmented fourth to a major third (C-E), which is the third and root of the C major tonic chord — a stable, consonant interval. This inward motion is what creates the characteristic feeling of closure at an authentic cadence: two dissonant notes simultaneously find their consonant resolution, converging on the heart of the tonic chord.
The resolution is overdetermined — two independent voice-leading principles both point toward the same motion. First, the leading tone (B) has an inherent upward tendency: it sits a half step below tonic and pulls toward it. This tendency exists independently of any tritone. Second, the chordal seventh (F) has an inherent downward tendency: as a dissonance within the chord, it resolves by falling to the nearest consonant tone. These two tendencies happen to combine into the inward contraction of the tritone, which is why V7-I feels doubly resolved — the harmonic tension of dominant function *and* the contrapuntal tension of the tritone dissonance are both satisfied in a single motion. This double satisfaction is why the dominant seventh became the most conclusive harmonic device in common-practice tonal music, and why understanding its tritone mechanics is essential for every aspect of voice leading that follows.
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