I would definitely try to keep in touch in a way where he doesn't need to respond. Like " this is song I like, I hope you like it too", did you notice? No question.
Then something else, something else, THEN a question, then a call, build up communication patterns...
oh!!! this is really different from what I was thinking... I was thinking about just waiting 3-4 weeks for him to call me before I do anything else. Since we went from 5 months of NC, to 6 minutes on the phone, then 3 weeks later 2 calls totalling 40 minutes, maybe I should give him space to make the next move? Can you tell me more why you suggested keeping in touch in a way that he doesn't need to respond? I am interested in your idea b/c it is so different than mine.