Thanks! The audio was rendered via a narration web service I wrote for the backend of my project. It took 12 seconds to narrate and generate metadata (used to highlight the word or sentence that's being spoken).
I'd be happy to set something up such that you could post the contents of a new post to a webhook, and it could respond with embed code immediately. Placing the embed code e.g. under the post title would load a small widget you could play the audio from.
It's also possible to tune the narration quality specifically for LessWrong so it uses the proper lexicon and more natural emphasis :)
I'm working on tech of the "quality text-to-speech" variety, especially for content that's longer than a few sentences, as a component of my project to make audio web browsing rich, delightful, and ubiquitous.
As an example, here's narration of this post: (Narration of Fading Novelty).
I do a lot of traveling, and love consuming information via audio. I'm actually working on technology for natural narration of web content. I'd be happy to create high quality narration for all content on the site that you can embed into post pages. Feel free to reply or contact me if you're interested :)
It'd be no problem to include speed control features in the first version, and text highlighting shortly thereafter (I already have this feature in my mobile app.)