MorphVOX Voice Changer Software can be used with Mumble.  Just follow the steps below.

1. Run MorphVOX Pro and make sure the "Listen" button is off so you do not hear your voice when talking.
2. Run Mumble.
3. Click on the "Configure" menu and select "Audio Wizard."
   
   
   
   
4. Click "Next" to skip the "Introduction" page.
5. On the "Device selection" page change the Input Device to "Microphone (Screaming Bee Audio)"
   
   
   
   
6. Click "Next" through the remaining pages.
7. Mumble should now use MorphVOX morphed voices.