1. Opening and Closing Chorale: Bach often began and ended his cantatas with a chorale. This provided a sense of unity and coherence to the work, as well as a thematic link between the different movements.
2. Interwoven Chorales: Bach sometimes wove chorale melodies into the fabric of other movements, such as arias and recitatives. This technique helped to unify the cantata on a deeper level, creating a sense of continuity and cohesion.
3. Chorale Fantasias: Bach composed chorale fantasias, which were extended instrumental treatments of chorale melodies. These fantasias often served as introductions or interludes between movements, and they helped to develop and explore the chorale melodies in a more improvisatory manner.
4. Chorale Variations: Bach also wrote chorale variations, which involved presenting a chorale melody in different variations, each with its own unique treatment and character. These variations could be used to explore different aspects of the chorale melody and to add variety to the cantata.
5. Cantus Firmus: In some cantatas, Bach used a chorale melody as a cantus firmus, which is a melody that is played or sung throughout the movement while other voices provide accompaniment. This technique provided a strong structural foundation for the movement and helped to unify the different sections.
By employing these various techniques, Bach was able to use chorale to unify his cantatas on multiple levels, creating a sense of coherence, continuity, and thematic unity throughout the work.