The four-part choir (Soprano, Alto, Tenor, Bass) is the ultimate musical sandbox. It offers infinite textural possibilities, yet it is bound by the strict laws of physics. Whether you are writing a Bach chorale or a pop arrangement, the rules of Voice Leading are the same. They exist not to annoy you, but to make the choir sound resonant. A well-written chord rings in the room; a poorly written chord sounds like mud.
Part 1: The Physics of Spacing (The Overtone Series)
Acoustics dictate that low notes take up more "sonic space" than high notes. If you play a Low C on a piano, you are actually hearing a series of overtones (C, C, G, C, E, G, Bb...). The lower overtones are spaced widely apart. The higher overtones are clustered together. To make a choir sound resonant, you must mimic this natural law.
The "Pyramid" Rule
- Wide at the Bottom: Intervals between Bass and Tenor can be large (up to an octave or a 10th). This leaves room for the harmonics of the bass note to "bloom."
- Tight at the Top: Put Soprano, Alto, and Tenor close together (often within an octave). They reinforce each other's upper harmonics.
- The Mud Zone: Never write thirds or fourths below C3 (the C below Middle C). It sounds like acoustic mud because the overtones clash violently.
Part 2: Doubling Rules (Who gets the extra note?)
A triad has 3 notes (C-E-G). You have 4 singers. Someone has to double up. Choosing the wrong note to double can destabilize the chord.
Root Position Chords
- Rule: Double the Root.
- Why: The root is the foundation. Doubling it makes the chord sound grounded and strong.
- Exception: You can double the 5th, but it sounds hollower. Never double the Major 3rd (it makes the chord sound shrill).
First Inversion (6/3) Chords
- Rule: Double the Soprano (notes with melodic interest) or the Bass.
- Why: First inversion chords are lighter. Doubling the bass (the 3rd of the chord) is usually allowed unless it is the Leading Tone. Never double the Leading Tone (Ti), because both voices will want to resolve up to Do, causing parallel octaves.
Second Inversion (6/4) Chords
- Rule: Always double the Bass (the 5th of the chord).
- Why: In a 6/4 chord (like a Cadential 6/4), the bass note is acting as a "dominant pedal." Doubling it emphasizes the suspension that is about to resolve.
Part 3: The "Forbidden" Parallels
Why did your theory teacher scream about Parallel Fifths? It's not because they are "ugly." It's because they are too "perfect."
The Borg Effect
When two voices move in parallel perfect 5ths, the ratio of their frequencies (3:2) is so simple that they acoustically blend into one thick sound.
- The Problem: You lose the independence of the lines. The 4-part choir suddenly sounds like a 3-part choir with one really thick voice. In Counterpoint, Independence is King.
- The Solution: Use Contrary Motion. if the Bass goes Up, the Soprano should go Down. This guarantees you won't have parallels and opens up the sound.
Direct (Hidden) Fifths
This is the sneaky cousin of the parallel fifth. It happens when the Bass and Soprano move in the same direction and land on a Perfect 5th, with the Soprano leaping.
- Why it's bad: It draws attention to the "hollowness" of the 5th.
- The Fix: Approach perfect intervals by contrary motion, or make sure the Soprano moves by step.
Part 4: Practical Workflow
Don't try to write all 4 parts at once. You will get stuck. Follow this hierarchy:
Step 1: The Melody (Soprano)
Write a killer tune. Make sure it has a good contour (an arch shape). It should be singable and memorable.
Step 2: The Foundation (Bass)
Write a strong bass line that makes harmonic sense.
- Tip: Try to move the bass in contrary motion to the melody. If the melody goes up, take the bass down. This creates a "shell" for the inner voices.
Step 3: The Filling (Alto/Tenor)
Now fill in the missing chord tones.
- The Lazy Singer Rule: Singers hate leaping. Keep the inner voices smooth. If a note is in the previous chord and the next chord, keep it in the same voice (Common Tone).
- Range Check: Just because a Tenor can hit a High A doesn't mean he wants to. Keep the inner voices in their comfortable middle register (Tessitura).
Part 5: The Final Checklist
Before you hit print, run this diagnostic on your score.
- The "Alto Boredom" Check: Is your Alto singing the note "D" for 12 measures in a row? If so, rewrite the voicing. Bored singers go flat.
- The "Tenor Strife" Check: Is the Tenor consistently singing above F4? He will get tired. Drop the key or change the voicing.
- The "Crossed Wires" Check: Did the Alto accidently dip below the Tenor? Voice crossing is confusing for the ear. Keep them in their lanes.
- The "Singability" Check: Sing every individual line a cappella. If it feels awkward to you, it will feel awkward to them.
Video Tutorial: Rules of Four-Part Writing
Professor Eric Lindsay breaks down the essential rules in this clear demonstration.
Conclusion
The rules of Next-Level Harmony are strict, but they are the ladder you climb to reach musical freedom. Once you understand why parallel fifths kill independence, you can choose to use them for effect (like in a rock anthem). But you must learn the rules before you can break them effectively.
You have mastered the notes. Now, let's look at the history regarding the masters of this craft. Next: The Renaissance Evolution.
About the Author
HaND. is a choral veteran with 15 years of experience in practice and organization. A primary Bass, HaND. also demonstrates exceptional versatility as a Countertenor and Vocal Percussionist.
