Embedding sound file in a PDF built with LaTeX letter class

[David Carlisle]

>From what I can glean from the documentation for "media9", it seems to require various plug-ins that look for external files, and there seems to be reliance on Flash, which is not good.

media9 is pretty much the standard package in this area.  Irrespective
of TeX interfaces, I'm not aware of any way to run sound files in a
PDF without using flash.

David