Since I work a lot with sound, and I'm constantly rummaging through all kinds of music software, I came up with a cool program that was made to communicate in online games by voice, but it is also compatible with IP telephony programs, VoIP and messengers (Skype, AIM, Yahoo, MSN, Google Talk, TeamSpeak, and others). The program deals with voice morphing. It changes beyond recognition in real time, and the original timbre is almost impossible to restore – you can disguise yourself well.
For serious work, integration with such audio processing monsters as Sound Forge, Vegas, ACID, Audacity, and many others is provided. There is a convenient compact mode of operation for working in messengers and games.
The voice changes on the fly, it can be applied not only to modulation, but also to all kinds of shifts, wrapping, not to mention the usual effects, such as echoes received in different virtual spaces, or background sounds (for example, as if you are in transport or in nature, where birds sing). It's a pity that the free trial is only seven days, I didn't have time to play enough. Now I'm thinking whether to buy it?
Pruflink: http://www.screamingbee.com/product/MorphVOX.aspx .