Hi, would it be acceptable if the audio files stayed in flash format? Flv files / a flash based player could be embedded in the emails. One benefit of this solution is that video messages would be an option with pretty much no extra difficulty.
The only other way I know of to create mp3 files (or even record audio) would be with a java applet, but unfortunately chrome doesn't support java on macs.
Apparently javascript webcam/microphone access will be part of HTML5, but as far as I know no one has implemented it yet.
Anyways, PM me if you are interested in the flash version / want to talk more about this.