The pattern in Bach’s first prelude seems quite simple, yet it incorporates a beautiful asymmetry, ascending 5 pitches and then 3. This prevents the piece from becoming dull on the surface. Below are some other representative pattern preludes:
Writing a pattern prelude
1. Choose a key and outline the structural bass
2. Add an opening pedal / formula, a descending or ascending line with a singing upper part, and a closing double cadence
3. Add expansion to the line using a sequence
4. Create modulations within the ascending or descending line.
5. Add any other expansion you wish to have.
6. Create a pattern and determine how many voices it represents
7. Write out the prelude as chord progressions.
8. Write out the full prelude with diminution.
Below are standard sequences you can use in your prelude