mikrosonic, developer of some of the most excellent Android apps have brought one of them, RoboVox - Voice Changer, to the iOS world. It's free, and I expect it's quite good fun too.
Here's the description:
Transform your voice with RoboVox and have your voice sound scary or funny, musical, evil or like a robot! RoboVox is a voice recorder and voice changing app using vocoder technology. Choose among 24 different voice styles and jam with the pitch and modulation settings by sliding your finger across the X-Y control field. Modify your voice live with your headphones on, record your voice and play it back transformed or use the parrot mode that repeats your altered voice automatically.
Save your recording, send it via email or share it directly on Facebook* or SoundCloud.
Get it now and alienate your voice!
- 24 voice models such as Pitch Shift (Chipmunk, Helium voice), Discobot, Badman, Exorcist, Bionic, Croack, Singing Robot, Dark, HAL, Stephen, Prophet
- X-Y control field for modifying pitch and modulation
- 3 different modes: real-time, parrot and recording
- Real-time mode (with headphones)
- Voice recording
- Share your results directly on Facebook* or SoundCloud
- Email your creations as WAV files
- Play RoboVox by connecting a MIDI keyboard
- Vocoder with real-time FFT spectral analysis