Harmonizing a scale involves creating a series of chords where each note of the scale serves as the root for a chord, with the remaining notes of that chord also derived exclusively from within the same scale. This process, known as diatonic harmonization, builds a complete set of chords naturally associated with that scale.
What is Scale Harmonization?
Scale harmonization is the process of building a set of chords from a particular musical scale. Instead of just a sequence of single notes, you create vertical sonorities (chords) that are inherently related to the scale's sound. This foundational concept in music theory is vital for composing melodies, creating accompaniments, and understanding harmonic progressions.
The Basic Process: Building Diatonic Chords
To harmonize a scale, you apply a consistent method to each degree of the scale:
- Identify the Scale: Choose the scale you want to harmonize (e.g., C Major, A Natural Minor).
- Use Each Note as a Root: Begin with the first note of the scale. This note becomes the root of your first chord. Then, move to the second note of the scale and use it as the root for the second chord, and so on, for every note in the octave.
- Build Chords Using Only Scale Tones: For each root note, construct a chord by stacking intervals (usually thirds) using only the notes available within the original scale.
- Triads (3-note chords): Most commonly, you build a triad by taking the root, the third above it, and the fifth above it, all counted within the scale. For example, if your root is C in the C Major scale, you'd take C (root), E (a third above C within the scale), and G (a fifth above C within the scale) to form a C Major chord.
- Tetrads (4-note chords): For richer harmonies, you can extend chords to four notes (seventh chords) by adding the seventh above the root, again, strictly using notes from the original scale.
The first chord built from the tonic (the first note of the scale) will typically be a I major chord when harmonizing a major scale.
Chord Qualities in a Major Scale
When you harmonize a major scale using triads, a consistent pattern of chord qualities emerges. These are typically represented by Roman numerals (uppercase for major, lowercase for minor, and ° for diminished).
| Scale Degree | Roman Numeral | Chord Quality | Example (C Major) | Notes (C Major) |
|---|---|---|---|---|
| 1st (Tonic) | I | Major | C Major | C-E-G |
| 2nd (Supertonic) | ii | minor | D minor | D-F-A |
| 3rd (Mediant) | iii | minor | E minor | E-G-B |
| 4th (Subdominant) | IV | Major | F Major | F-A-C |
| 5th (Dominant) | V | Major | G Major | G-B-D |
| 6th (Submediant) | vi | minor | A minor | A-C-E |
| 7th (Leading Tone) | vii° | Diminished | B diminished | B-D-F |
This predictable sequence (Major, minor, minor, Major, Major, minor, diminished) is fundamental to understanding Western harmony.
Chord Qualities in a Natural Minor Scale
Similarly, the natural minor scale also yields a specific pattern of diatonic triads:
| Scale Degree | Roman Numeral | Chord Quality | Example (A Natural Minor) | Notes (A Natural Minor) |
|---|---|---|---|---|
| 1st (Tonic) | i | minor | A minor | A-C-E |
| 2nd (Supertonic) | ii° | Diminished | B diminished | B-D-F |
| 3rd (Mediant) | III | Major | C Major | C-E-G |
| 4th (Subdominant) | iv | minor | D minor | D-F-A |
| 5th (Dominant) | v | minor | E minor | E-G-B |
| 6th (Submediant) | VI | Major | F Major | F-A-C |
| 7th (Subtonic) | VII | Major | G Major | G-B-D |
Practical Application and Importance
Harmonizing scales is more than just a theoretical exercise; it's a practical skill with significant applications:
- Songwriting and Composition: It provides a ready-made palette of chords that naturally sound good together, helping composers create cohesive and melodically rich pieces.
- Accompaniment: Musicians can use diatonic chords to accompany melodies, knowing which chords will fit the key.
- Improvisation: Understanding the underlying harmony allows improvisers to choose notes and arpeggios that complement the chord progression.
- Analysis: It helps in analyzing existing music, understanding why certain chords are used and how they relate to the prevailing key.
By understanding how to harmonize a scale, musicians unlock a deeper comprehension of musical structure and unlock creative possibilities in their playing and composing.
