part-writing rules

what should you do when root moves by a fifth?

a. keep a common tone

b. change structure if there is a common tone

c. if no common tone, keep same structure and move all 3 upper voices in same direction

what should you do when root moves by a third?

keep same structure and keep two common tones

what should you do when root moves by a second?

a. soprano moves in contrary motion to the bass

b. keep same structure and move all 3 upper voices in same direction

c. if soprano moves same direction as bass, you will need to use irregular doubling, usually on the second chord of the pair

how to create a chord with irregular doubling:

to create a chord with irregular doubling, double the soprano note in either alto or tenor