Here's another one I want to try for a long time but still haven't (to have a single, animated SVG file, still copy-pastable): https://github.com/nbedos/termtosvg .
A tutorial using asciinema in action.
https://asciinema.org/a/188659
You can't add voice into asciinema itself but a asciinema recording URL would be an excellent handout material (like powerpoint) to give to students. Your students can view Terminal action with very clear text, unlike videos where reading text can be difficult.
Even if you use other method for recording/delivering your voice/audio lecture, including Asciinema replay link would be a huge benefit to students.
I think it's excellent but it is limited to just the terminal. I don't think it's possible to incorporate a voiceover or soundtrack which you may sometimes want to do.