can you put sound in tads two and three?

if so how?

Yep, it’s possible. Documentation can be found in the TADS 3 Bookshelf:

(“Introduction to HTML TADS”, at the bottom of the page.)

Note that between MP3 and Ogg Vorbis, the latter is preferred. Here’s why:

With Vorbis you get a much higher audio quality at a much lower file size. Vorbis audio is also safer to use, because some popular Linux distros are disabling MP3 support when shipping QTads in order to avoid infringing the MPEG patents (you are required to pay royalties to use the MP3 format, even in software that is open source), which would result in no sound at all on those systems.

As for possible limitations mentioned in the article, the info is a bit outdated. All currently existing multimedia 'terps do not have a limit to the amount of layers playing simultaneously, and fades and cross-fades are supported everywhere.