The process of scoring music for four voices, as in a hymn or chorale, was governed by some basic principles in the common practice period. Here are some general guidelines that most arrangers have followed for smooth voice-leading:
1. Retain common tones between chords in the same voice.
2. Move by step to the nearest chord tone, if possible.
3. Move by consonant leaps, avoiding augmented or diminished intervals.
4. Keep the range of each voice in mind, and do not cross voices above or below each other.
5. Stay within an 8ve between upper voices. Wider intervals are fine between bass and tenor.
6. Follow the figured bass indications for inversions.
Here are a few more specific guidelines to keep in mind:
1. A parallel P5 or P8 between two voices in similar or contrary motion is avoided.
2. Resolve the minor 7th of any chord down by step.
3. Inversions of dominant sevenths should be complete chords.
4. Avoid an augmented 2nd leap between the minor 6th and major 7th in minor keys.
5. When writing incomplete chords, omit the 5th (never omit the 3rd).
6. In root position major triads, it is preferable not to double the third.
7. In the soprano or bass part, the major 7th (leading tone) resolves up to the tonic.
8. Raise the 7th in minor keys to form a major V chord or vii⁰ chord.
9. Include Roman Numerals and figured bass below your realization.
10. For independent parts, use a combination of contrary, oblique and similar motion.
The term "doubling" refers to a note that appears twice when a triad with three notes is scored in four parts. It may be at the unison or octave. Here are some guidelines applied to doubling, and to inverted chords in four part writing:
1. Use four voices in each chord. The doubled note may be an 8ve or unison.
2. Root position: double the Bass.
3. First inversion: double the Tonic, 4th, or 5th scale degree of the key.
4. Second inversion: double the Bass.
5. Leading Tone diminished (vii⁰): double the 3rd, or the 5th if it is in the Soprano voice.
6. Do not double the Leading Tone of the key.
7. To avoid parallelism, the root may be tripled and the 5th omitted.
Refer to Guidelines for Voice-Leading.