Have you thought about the avenue of adding the text as if it was ‘lyrics’? If so, It’s quite possible to do so, though you would have to distribute the audio along with the lyrics.

All the details on how to add synchronised lyrics to an audio using WMP11 file can be found here:
http://www.microsoft.com/windows/windowsmedia/knowledgecenter/howto/AddLyrics.aspx

The funky thing about it all is – since you are editing ID3v2 tag, it will be compatible over players such as WMP11, Winamp, Itunes, etc. For a full list of players, see -
http://www.id3.org/Implementations

I mean like if your theory is for us to see the text of the audio whether moving or like in a subtitle process, wouldn’t it need to be in a picture like manner, a.k.a. a video? To my knowledge to show anything moving on-screen (whether text or subtitles) would need to be a video, an image (i.e. .gif) or even extremely futuristic where we could just see moving text (whether scrolling or subtitle like manner) via our own eyes or special glasses. I know the special glasses idea has been thought of, but I don’t know whether it’ll be put for any good use, aside from geeky movies. And how would we listen to the audio in this method? The same as we usually do for on-the-go music, with headphones, earphones, etc.

Aside from that, how would you like it to be used in? On an PMP or PC? If PC, the only method I can think of is the same as edo pointed out, “audio drama cd’s in video format.” If for on-the-go, the special glasses method as I pointed out, a virtual reality method in which, where ever you travel you can see the texts as long as you are listening the the audio – way too advanced for the real world, or a simpler scrolling/subtitle-like manner on the PMP itself, but not as a video – sort of like how on old Sony MP3 players you can see the name of the song on the display name area and they scroll.

I hope anything I’ve mentioned can help us have a better understand of what you are trying to figure out or do. Feel free to email me for anything you’d like me to explain/broaden further (as I personally don’t like to write paragraphs of information for blog comments).

The closest I’ve thought of will be something like this:

http://www.youtube.com/profile?user=bluedragoon

His videos with the Haruhi drama CD, or my own YT channel with the Lucky Star drama CD. But it seems you do not want to go down this route.

A CD+G maker: http://www.powerkaraoke.com/src/prod_karaokecdgcreator.php

sice it’s like almost an standar maybe it whould work.

hope it helps, bb :)

PS: excuse my bad english :P

@notaname: Most players would play audio only and just ignore the subtitles.

On the outlandish prospect of created a new format (or extension to a format): in the same way test in .ass can be styled (and often abused to give individual characters their own distractingly FABULOUS text colours), maybe associate a ’style’ with each character’s lines, and instead of colouring the text instead pop up a portrait of the character (with fallback of a blank box). Maybe a similar thing for ’scenes’ to stick up a background. Then again, this all requires EFFORT to code in the first place, more EFFORT to add when translating/timing, and clutters up the screen. So text-on-a-black-box is probably the way to go.