But how do you organize and recall the transient discussion that happened on a call? Hint: an email summary, or some kind of summary document. And the latter also works with long email chains.

My personal experience is that emails and written documents are how things actually get done, but sometimes we have to go through voice calls and in-person meetings in order to get that far.

Those voice interactions felt like some sort of psychological barrier that couldn't be bypassed any other way, at least initially, but once I have opened up a non-voice channel, that's what we tend to use going forward.