As many here know, I have got this thing about using a minor pent in blues soloing where 3 has a substitute 2, and 7 has a substitute 6. Since these are substitutes, I propose that 3 cannot directly precede or follow 2. Ditto with 7 and 6. I wrote out some scale-like patterns that use this rule. Notice that they overall pitch content is equal to a dorian mode. The patterns below are in C blues. They are descending for the important reason that fast scale-like runs in blues solos tend to descend, not ascend. I believe this is because going up with anything requires more effort than going down, due to the effects of gravity. I believe that the concept of melodic gravity plays an important role in blues. To test my hypothesis, the first step would be to listen to a bunch of blues solos and see if the faster, scale-like stuff is generally descending, often quickly. In contrast, ascending music ascends over a greater amount of time, and is often stopping and starting.