If you want voiceover and more you might wanna check out CodeMic.io.

That's not just proprietary, it's surveillance capitalism. "Subscribe for early access and monthly progress updates." You should be embarrassed for posting that kind of filth on a thread about asciinema, which is a free-software program that works offline and has strict privacy protections.

Also, codemic.io seems to be oriented toward full-motion video, so aside from the authoritarianism issues, it's not even related.