I found some interesting stuff inside Corona SDK, and possibly a way to modify pitch but I haven't figured out how to use it yet:
http://www.yobonja.com/journal/2011/5/25/hidden-audio-module-in-corona-sdk.html

If someone can figure out how to use it, making those 'Talking Tom' type apps could be possible in Corona along with a lot of other applications.

-Angelo

Cool!!!

HAH!! Nice find = ) Eric's comment is awesome. I hope we hear something neat soon.

We just posed a blog entry response for this:
http://blog.anscamobile.com/2011/07/the-secretundocumented-audio-apis-in-corona-sdk/