Add the ability to mask a voice in recordings

[Redmayspecial]

User Story

As a translator I would like to have my voice masked so that I cannot be recognized by my voice, yet the recording is clear to the hearer.

From Doug Schreiber...
We've been on a long quest to find voice masking software for doing oral
BT here in China, a secure access country. It is risky for the
minorities to do the recording lest they be found out and persecuted in
some way.

I've worked with a brother in SIL here to identify potential apps. The
most promising (and expensive) was FLUX but I found it took a very
powerful PC to work (more than my SurfacePro3) and the masking was not
quite what I had hoped for - especially for $300+. I found it also a bit
difficult to figure out how to tune the voices, etc. other than using
the presets.

I happened upon AV Voice Changing Software Diamond.
(http://www.audio4fun.com http://www.audio4fun.com/) for $100*. I
first tried it myself by masking my own voice then sending it to my
family. Since it sounded a lot like my sister so I pretended that it was
a podcast of someone who sounded like my sister and asked them to
confirm. They fell for it. The quality is not crystal clear and sounds a
bit tinny (sample attached), like over a cell phone, but they didn't
know it was me. I created the attached manual and gave it to the
Pomegranate team to test and they agreed that it appears to be decent.

Though we have not started using in production, I wanted to get it out
there in case there were others in similar situations who have been
requesting help. If you want to refer them to me for more info., I'd be
glad to help as I can.

*I searched online and found a $25 discount; not sure it if's still
available.

Doug