Steps to Harmonizing a Soprano Melody

Identify the key.

Identify the cadences at phrase endings.

Decide on the type of voicing: Keyboard, Choral Close, Choral Open. Mixed spacing can be employed if the soprano has one or more large leaps, or if it moves into a particularly high or low register.

Write out the most obvious formulas leading to the cadences.

Harmonize the soprano line using standard chord progressions. Do not overcomplicate. Focus on obvious diatonic materials first.

Once the harmonization is complete, consider the use of nonharmonic tones to enhance the voices, but do not overcomplicate.

Do not be content with the first draft. Continue to check and revise.