Meet the Boss VT-1: a voice transformer that lets you change tone, pitch, and other audio settings. It has 4 slicer controls for real-time adjustments. It can be installed in seconds. Just remove your handset and plug the device into the handset plug using the modular jack cable.
The unit has a microphone / earpiece for handsfree use. It gives you full control over timbre, tone, formant, reverberation, and pitch.
[where to get it]