4-2-1 Construction Explained

Key Concepts

4-2-1 Construction in music refers to the process of building chords and harmonic structures using specific intervals. Key concepts include:

• Triads: Basic three-note chords built on the intervals of a third and a fifth.
• Seventh Chords: Four-note chords built on the intervals of a third, a fifth, and a seventh.
• Inversions: Rearrangements of chord notes to change the bass note.

Triads

Triads are the simplest form of chords, consisting of three notes: the root, third, and fifth. They can be major, minor, diminished, or augmented depending on the intervals between the notes.

Example: A C major triad is built from the notes C (root), E (third), and G (fifth). The intervals between C and E are a major third, and between E and G are a minor third.

Seventh Chords

Seventh chords add an additional note to the triad, creating a four-note chord. This additional note is the seventh, which can be major, minor, or diminished. Seventh chords provide more harmonic richness and tension.

Example: A C major seventh chord includes the notes C (root), E (third), G (fifth), and B (major seventh). The intervals are a major third, a minor third, and another major third.

Inversions

Inversions change the bass note of a chord by rearranging the notes. For triads, there are three inversions: root position (root as the bass note), first inversion (third as the bass note), and second inversion (fifth as the bass note). For seventh chords, there are four inversions.

Example: For a C major triad, the first inversion would be E-G-C, and the second inversion would be G-C-E. For a C major seventh chord, the first inversion would be E-G-B-C, and so on.

Analogies

Think of triads as basic building blocks in a construction project. Just as bricks form the foundation of a building, triads form the foundation of harmonic structures. Seventh chords are like adding extra floors to the building, providing more complexity and height.

Inversions can be compared to rearranging furniture in a room. Just as moving furniture changes the layout and functionality of a room, changing the bass note of a chord changes its harmonic function and sound.