Leading Tone in Minor Keys: Altered Leading Tones and Harmony

📚 Understanding the Leading Tone in Minor Keys

In music theory, the leading tone is the note immediately below the tonic (the root of the key). It has a strong tendency to resolve upwards to the tonic, creating a sense of resolution and closure. In major keys, the leading tone is a diatonic note, meaning it naturally occurs within the key's scale. However, in minor keys, the seventh scale degree is a whole step below the tonic. To create a leading tone in minor, we often raise this seventh degree by a half step.

📜 Historical Context

The use of the leading tone to create a strong cadence dates back centuries. Composers in the Baroque and Classical periods frequently employed this technique to emphasize the tonic and provide a satisfying resolution. The raised leading tone in minor keys became a standard practice to mimic the strong pull towards the tonic that was already present in major keys.

🔑 Key Principles

• 🎼 The Natural Minor Scale: The natural minor scale follows the formula: root, 2, b3, 4, 5, b6, b7. Notice the lowered seventh (b7).
• ⬆️ The Harmonic Minor Scale: To create a leading tone, the seventh degree is raised by a half step. This creates the harmonic minor scale: root, 2, b3, 4, 5, b6, 7.
• 🎵 The Melodic Minor Scale: In classical theory, the melodic minor scale has an ascending and descending form. Ascending: root, 2, b3, 4, 5, 6, 7. Descending: root, b7, b6, 5, 4, b3, 2, root (same as natural minor).
• 🔗 Resolution: The raised leading tone creates a half-step interval between the 7th and 8th (octave) which gives a strong feeling of resolution to the tonic.

🎸 Real-World Examples

Let's consider the key of A minor:

• 🎹 Natural Minor: A, B, C, D, E, F, G
• ✨ Harmonic Minor: A, B, C, D, E, F, G#

In A harmonic minor, G# becomes the leading tone, resolving up to A.

Altered Leading Tones and Harmony

Sometimes, composers use altered leading tones to create unique harmonic effects. Instead of simply raising the seventh degree, they might use other chromatic alterations to create tension and interest.

💡 Examples of Altered Leading Tones

• ♭ bII (Neapolitan Chord): The Neapolitan chord, built on the lowered second degree, often functions as a substitute for the dominant, resolving to the tonic. For example, in C minor, the Neapolitan chord would be Db major.
• ⅘ Augmented Chords: Augmented chords built on the leading tone can create a strong, dissonant pull towards the tonic. For example, in A minor, a G# augmented chord (G#-B#-D#) can resolve to A minor.

🎼 Harmonic Implications

The altered leading tones can significantly impact the harmony of a piece. They introduce chromaticism, which can add color and complexity to the music. These alterations often create a stronger sense of expectation and resolution when the music finally returns to the tonic.

🧮 Mathematical Explanation

The interval between the leading tone and the tonic is crucial. In equal temperament, a semitone is approximately $2^{\frac{1}{12}}$ of an octave. This small interval creates a strong pull towards the tonic, dictated by the mathematical relationships between frequencies.

📊 Table of Leading Tones in Minor Keys

📝 Conclusion

The leading tone is a fundamental element in creating strong tonal relationships, especially in minor keys. By understanding how to raise the seventh degree and how to use altered leading tones, you can add depth and complexity to your compositions and improvisations. Experiment with these concepts to unlock new harmonic possibilities in your music!