Minor Third Interval: The Heart of Minor Harmony

Summary:

The minor third interval, a span of three semitones, is the essential building block of minor harmony. It provides the melancholic, introspective, and soulful character that defines minor chords, scales, and keys. Understanding this interval is fundamental to grasping musical emotion and structure in virtually all genres.

Keywords:

Minor third, music interval, three semitones, minor chord, music theory, harmony, emotional expression, ear training, interval recognition, minor scale, blues music.

Introduction: The Sound of Emotion

What gives a song its feeling of melancholy, contemplation, or gentle sadness? More often than not, the answer lies in the minor third interval. As one of the most expressive intervals in music, the minor third is the cornerstone of the "minor" sound that distinguishes countless iconic melodies and chord progressions. Spanning exactly three semitones (or one-and-a-half steps), this humble interval is the DNA of minor harmony.

While its counterpart, the major third, often conveys brightness and joy, the minor third introduces a world of emotional complexity. It creates a gentle tension and a sense of depth that composers have used for centuries to evoke introspection, drama, and soulfulness. From the haunting refrains of classical music to the gritty riffs of the blues, the minor third is a powerful tool for musical storytelling.

Deconstructing the Minor Third

An interval in music measures the distance between two pitches. The minor third is defined by its specific size:

• Distance in Semitones: 3 semitones (e.g., on a piano, three adjacent keys, including black keys).
• Distance in Steps: 1 whole step + 1 half step (1.5 steps).
• On the Staff: It always spans three staff positions (e.g., a line to the next line, or a space to the next space).
• Cents: 300 cents in equal temperament, the standard tuning system.
• Frequency Ratio: Approximately 6:5 in just intonation, a simpler and more consonant ratio than the major third's 5:4, yet perceived as "darker" in a tonal context.

The most crucial distinction is that the minor third is one semitone smaller than a major third. This single semitone difference is responsible for one of the most significant emotional shifts in music.

The Foundation of Minor Chords and Scales

The minor third's primary role is to define minor chords. A minor triad is built with a root, a minor third, and a perfect fifth. The interval from the root to the third is what makes the chord "minor."

• Minor Triad (i) : Root + Minor Third + Perfect Fifth (e.g., C-Eb-G)
• Minor Seventh Chord (i7): Root + Minor Third + Perfect Fifth + Minor Seventh (e.g., C-Eb-G-Bb)
• Diminished Triad (vii°): Root + Minor Third + Diminished Fifth (e.g., B-D-F)

Notice how the minor third is a common ingredient. Without it, the entire landscape of minor harmony would disappear. The following example shows how a C minor triad is built from a minor third (C-Eb) and a major third (Eb-G), and how adding another minor third on top (G-Bb) creates a C minor seventh chord.

Building Minor Chords with Minor Thirds

The Minor Third in Melodies Across Genres

The minor third's emotional weight is not limited to chords; it's a powerful melodic tool used to craft memorable tunes.

Classical Music:

Composers like Bach and Chopin were masters of minor tonality. The opening motif of Beethoven’s Symphony No. 5 famously uses descending thirds, while his piece Für Elise opens with a vacillation between a minor second and a minor third, creating its signature yearning quality.

Blues and Jazz:

The minor third is the heart of the blues. The "blue note" is often a "bent" or "worried" note that hovers between the minor and major third, creating the raw, expressive sound central to the genre. In jazz, the minor third is essential for outlining minor and diminished harmonies during improvisation.

Popular Music:

The minor third is everywhere in pop, rock, and folk music. Think of these iconic melodies:

• "Greensleeves" / "What Child Is This?": The first two notes ("Alas, my") form an ascending minor third.
• "Mad World" (Tears for Fears): The vocal melody is steeped in minor-key melancholy, heavily featuring the minor third.
• "Losing My Religion" (R.E.M.): The iconic mandolin riff is built around a motif that outlines a minor third.
• "Smoke on the Water" (Deep Purple): The legendary guitar riff is famously constructed from parallel fourths, but the underlying scale it implies is the blues scale, which features a minor third.

Ear Training: How to Recognize a Minor Third

Training your ear to instantly recognize the minor third is a vital skill for any musician. The most effective method is to associate the interval with the opening notes of a famous song.

• Ascending Minor Third:
  • "Greensleeves" ("A-las...")
  • "Brahms' Lullaby" ("Lul-la...")
  • "O Canada" ("O Can...")
• Descending Minor Third:
  • "Hey Jude" (The first two notes of "Hey...")
  • "The Star-Spangled Banner" ("Oh-oh say...")
  • "Frosty the Snowman" ("Fros-ty...")

Practice Exercise: Spot the Minor Third

Listen to the following pairs of notes. The first two are minor thirds, and the last two are major thirds. Can you hear the difference in their emotional quality?

Practical Applications for Musicians

For Composers and Songwriters:

Use the minor third to instantly shift the emotional mood of a piece. A simple change from a major third to a minor third in a melody or chord can introduce a feeling of introspection or sadness. It's also a key tool for modulating between relative major and minor keys (e.g., C Major and A Minor) , creating a seamless and satisfying harmonic journey.

For Performers and Improvisers:

Intonation is key. On instruments like violin or with the voice, the "sweetness" of a minor third is often found by playing it slightly lower than its equal-tempered position. Pay attention to how the minor third functions within a chord—as the third of a minor chord, it defines the quality; as the fifth of a diminished chord, it adds instability.

Advanced Concepts

Inversion: The Major Sixth

Every interval has an inversion, which is created by moving the lower note up an octave. The inversion of a minor third (3 semitones) is a major sixth (9 semitones). It's a fascinating transformation: the close, melancholic sound of the minor third becomes the open, uplifting sound of the major sixth.

Enharmonic Spelling: Minor Third vs. Augmented Second

While C to Eb is a minor third, what about C to D#? On a piano, they are the same keys, but theoretically they are different. Intervals get their number (second, third, fourth) from the letters they span. C to D is a 'second', so C to D# is an augmented second. C to E is a 'third', so C to Eb is a minor third. The correct spelling depends entirely on the musical key and harmonic context.

Notational Difference: C-Eb vs. C-D#

Conclusion: The Soul of Harmony

The minor third is far more than just a theoretical concept; it is an elemental force in music that shapes how we feel and what we hear. Its ability to define minor harmony, create poignant melodies, and add emotional depth makes it indispensable to musicians of every skill level and background.

By learning to identify, understand, and utilize the minor third, you unlock a deeper level of musical literacy. You gain insight into the structure of your favorite songs and acquire a powerful tool for your own creative expression. So listen closely for that beautifully melancholic sound—it’s the minor third, working its magic.

References:

1. Aldwell, E., Schachter, C., & Cadwallader, A. (2018) . Harmony and Voice Leading (5th ed.). Cengage Learning.

2. Benward, B., & Saker, M. (2015). Music in Theory and Practice (9th ed.). McGraw-Hill Education.

3. Karpinski, G. (2017). Manual for Ear Training and Sight Singing. W. W. Norton & Company.

4. Kostka, S., & Payne, D. (2018). Tonal Harmony: With an Introduction to Post-Tonal Music (8th ed.). McGraw-Hill Education.