When improvising over E Minor (Aeolian or Dorian) I frequently find my self playing ideas based on Em and D triads. I usually don't spell them out so rigorously as this example but, I thought the idea and the example of open forms was worth posting. I usually do this with close voice forms as well. The actual improvising part is more random, less structured. So this example is open voice Em and D alternating ascending up the neck.