Those can work, I’ve started doing youtube live presentations but without live audience those are sort of more like long-winded voice messages have posted few 1/2 hour talks plan to do more of those always lots to talk about.
One challenge if using short voice messages going back and forth is conversation can be limited by people’s attention span, same as people will start to skim over if there’s any more than two paragraphs of text in a post and usually only respond to one sentence at best.
Voicemail is good for being able to leave voice message if can’t answer the phone.