Realization, also known as voice leading or part writing, is the precise position of different voices contributing to a harmony. Sequences of the same chords may be realized in various satisfactory/unsatisfactory ways. To achieve the best results, the guidelines listed below and explained in later articles are the result of the several centuries of experience.
Summary
1. Choose position neither too tight nor wide.
2. Preferably double the fundamental.
3. Only double the third when needed & this note is a good note of the tone (1st, 4th, 5th.)
4. Never double in unison.
5. Preferably suppress the fifth of the chord.
6. Never suppress the third.
7. Proceed as much as possible by the least disjointed intervals, especially in four parts.
8. Do not leap by an interval greater than the minor sixth, the octave excepted.
9. Sensible note always goes up to the tonic in the minor mode.
10. Only make a perfect fifth/octave from a direct movement when the upper part moves by conjoined degrees & the lower by disjointed degrees.
11. Two consecutive perfect fifths or octaves are absolutely forbidden, even by contrary movement.
Old Music Theory 