I find that blackboard oriented lectures are much more conducive to audience/lecturer communication because during blackboard oriented lectures going off the ra

I find that blackboard oriented lectures are much more conducive to audience/lecturer communication because during blackboard oriented lectures going off the rails is seamlessly natural, while that could not be further from the case with powerpoint oriented lectures. Overhead projector lectures are the best of both worlds. You can make pre-prepared foils but modify them on the fly, and create new ones on the fly as naturally as you can write on a blackboard.