You can pass Espeak recordings around legally. It's just GPL. The license applies to the software, not the content produced via it.
I will attempt to remember and find the time to take my demo recording of this on Rust compiler source code that's currently in dropbox and put it up somewhere more permanent. I doubt Dropbox will care for me much if I allow HN-volume traffic to hit my account. It's Espeak using an NVDA fork with an additional voice that some of us like, so vanilla espeak is in the ballpark.
What I don't remember is if vanilla non-libsonic espeak softcaps the speech rate. It might. I believe new versions of espeak integrate libsonic directly, but that old versions just silently bump the speaking rate down if it's over the max. I haven't used command line espeak directly for anything in a very long time.
Libsonic is an optimized library specifically for the use case of screen readers that need to push synths further: https://github.com/waywardgeek/sonic
There is a range slider that maxes as 450, which is the maximum speed according to the manual.
I tried listening to a Wikipedia article at 450, I am so amazed you can comprehend that. Perhaps that's equivalent of me visually scanning the text instead of reading, however when I do that, I tend to focus on interesting parts for long stretches of time. With espeak, how do you focus? Can you pause it at will?
Screen readers have a lot of commands for reading different sized chunks of content. In general there's probably around 50 keystrokes I use on a daily basis. It's not as straightforward as reading from top to bottom, though it can be. I can usually do a Wikipedia article without pausing at 450 or so.
As an interesting sidenote, screen readers have to co-opt capslock as a modifier key, then there's fun with finding keyboards that are happy to let you hold capslock+ctrl+shift+whatever.
